CCFNB Bancorp (CCFN) 424B3Prospectus supplement

Filed Pursuant to Rule 424(b)(3)
Registration No. 333-273023

To the Shareholders of CCFNB Bancorp, Inc. and Muncy Bank Financial, Inc.

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

On behalf of the boards of directors of CCFNB Bancorp, Inc., which we refer to as CCFNB, and Muncy Bank Financial, Inc., which we refer to as MBF, we are pleased to enclose the accompanying joint proxy statement/prospectus relating to the proposed merger of CCFNB and MBF, and a special meeting to be held by each of CCFNB and MBF at which you will be asked to take certain actions as a holder of CCFNB common stock or as a holder of MBF common stock, as applicable, relating to the proposed merger.

At the special meetings, CCFNB’s and Muncy’s shareholders will each be asked to approve an Agreement and Plan of Merger, dated April 17, 2023 and as amended June 21, 2023, which we refer to as the merger agreement, between CCFNB and MFB pursuant to which MBF will merge with and into CCFNB, with CCFNB as the surviving entity, which transaction we refer to as the merger. Immediately following the merger, The Muncy Bank and Trust Company, a Pennsylvania chartered bank and trust company and a wholly-owned direct subsidiary of MBF, which we refer to as Muncy Bank, will merge with and into First Columbia Bank & Trust Co., a Pennsylvania bank and trust company and a wholly-owned subsidiary of CCFNB, which we refer to as FCBT, with FCBT as the surviving bank. We refer to the merger of Muncy Bank and FCBT as the bank merger. We collectively refer to the merger and the bank merger as the mergers. In connection with the merger, CCFNB will change its name to “Muncy Columbia Financial Corporation” and, in connection with the bank merger, FCBT will change its name to “Journey Bank.”

At the effective time of the merger, MBF shareholders will receive 0.9259 shares of CCFNB common stock for each share of MBF common stock they own, which we refer to as the exchange ratio, subject to the payment of cash in lieu of fractional shares. We refer to the CCFNB shares and cash to be received by MBF shareholders in the merger as the merger consideration. Based on the $40.05 closing price of CCFNB’s common stock on OTC Pink on April 17, 2023, the last trading day before the public announcement of the merger, the exchange ratio represented approximately $37.08 in value for each share of MBF common stock, representing merger consideration of approximately $59.6 million on an aggregate basis. Based on the $40.50 closing price of CCFNB common stock on OTC Pink on August 15, 2023 (the latest practicable trading day before the printing of the accompanying joint proxy statement/prospectus), the exchange ratio represented approximately $37.50 in value for each share of MBF common stock, representing merger consideration of approximately $60.3 million on an aggregate basis. Although the number of shares of CCFNB common stock that holders of MBF shares will be entitled to receive for each MBF share owned is fixed, the market value of the merger consideration will fluctuate with the market price of CCFNB common stock and will not be known at the time CCFNB and MBF

shareholders vote on the merger. However, as described in more detail in the joint proxy statement/prospectus, under the terms of the merger agreement, MBF may terminate the merger agreement if both (i) the average price of CCFNB common stock over a 30 day period ending on the date all regulatory approvals are received (excluding closing sale prices for trading days with less than 100 shares traded), which we refer to as the determination date market price, is less than $35.24, and (ii) the ratio of the determination date market price to $44.05, which we refer to as the CCFNB starting price, is more than 20% less than the ratio of the average of the NASDAQ Bank Index Value over the same 30 day period to the Nasdaq Bank Index Value on April 17, 2023; provided that CCFNB shall have the right to increase the conversion ratio such that the aggregate merger consideration, based upon the determination date market price, would satisfy this market termination test.

CCFNB shareholders will continue to own their existing shares of CCFNB common stock. The value of the CCFNB common stock at the time of completion of the merger could be greater than, less than or the same as the value of CCFNB common stock on the date of the accompanying joint proxy statement/prospectus. We urge you to obtain current market quotations of CCFNB common stock (OTC Pink trading symbol “CCFN”) and MBF common stock (OTCQB trading symbol “MYBF”).

We expect the merger will qualify as a reorganization for federal income tax purposes. Accordingly, MBF shareholders generally will not recognize any gain or loss for federal income tax purposes on the exchange of shares of MBF common stock for CCFNB common stock in the merger, except with respect to any cash received by such holders in lieu of fractional shares of CCFNB common stock.

Based on the exchange ratio and the number of shares of MBF common stock outstanding, CCFNB expects to issue approximately 1,489,179 million shares of CCFNB common stock to MBF shareholders, in the aggregate, in the merger. We estimate that former MBF shareholders will own approximately forty-two percent (42%), and existing CCFNB shareholders will own approximately fifty-eight percent (58%), of the common stock of CCFNB following the completion of the merger.

CCFNB and MBF will each hold a virtual special meeting of its respective shareholders in connection with the merger. At its respective special meetings, in addition to other business, CCFNB and MBF will ask their respective shareholders to approve the merger agreement. Both CCFNB and MBF shareholders will also be asked to vote on a proposal to approve one or more adjournments of their respective special meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the applicable special meeting to approve the merger proposal, which we refer to as the CCFNB adjournment proposal and the MBF adjournment proposal, respectively. In addition, MBF shareholders will also be asked to vote on a proposal to approve, on a non-binding, advisory basis, the compensation that may be paid or become payable to MBF named executive officers that is based on, or otherwise relates to, the transactions contemplated by the merger agreement, which proposal we refer to as the compensation proposal. Information about these meetings, the mergers and the other proposals to be voted upon is contained in this document. We urge you to read this document carefully and in its entirety.

The special meeting of MBF shareholders will be held virtually via the Internet on October 3, 2023 at 9:30 a.m., Eastern Time.

The special meeting of CCFNB shareholders will be held virtually via the Internet on October 3, 2023 at 11:00 a.m., Eastern Time.

Your vote is very important. Whether you are a shareholder of CCFNB or of MBF, to ensure your representation at the applicable special meeting, please complete and return the enclosed proxy card or submit your proxy by telephone or through the Internet. Please vote promptly. Submitting a proxy now will not prevent you from being able to vote at the special meeting. If you hold your shares in “street name” through a broker, bank or other nominee, you should follow the directions provided by your broker, bank or other nominee regarding how to instruct your broker, bank or other nominee to vote your shares. Without those instructions, your shares will not be voted and will not count toward the achievement of a quorum so that business can be conducted at the special meeting of CCFNB or MBF, as applicable.

Each of our boards of directors unanimously approved the merger agreement and the mergers, and determined that the merger agreement and the mergers are fair to, and in the best interests of, each company’s respective shareholders and other constituents. The board of directors of each of CCFNB and of Muncy unanimously recommends that holders of their common stock vote “FOR” each of the proposals to be considered at the respective special meetings. We strongly support this merger of our companies and join our boards in their recommendations.

This joint proxy statement/prospectus provides you with detailed information about the merger agreement and the mergers. It also contains information about CCFNB and MBF and certain related matters. You are encouraged to read this joint proxy statement/prospectus carefully. In particular, you should read the “Risk Factors” section beginning on page 46 for a discussion of the risks you should consider in evaluating the merger and how it will affect you. You can also obtain information about CCFNB and MBF from documents that have been filed with the Securities and Exchange Commission that are incorporated into this joint proxy statement/prospectus by reference.

On behalf of the CCFNB and MBF boards of directors, thank you for your prompt attention to this important matter.

Sincerely,

		Lance O. Diehl		Robert J. Glunk
		President and Chief Executive Officer CCFNB, Bancorp, Inc.		Chairman, President and Chief Executive Officer Muncy Bank Financial, Inc.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with the merger or determined if this document is accurate or complete. Any representation to the contrary is a criminal offense.

The securities to be issued in the merger are not savings or deposit accounts or other obligations of any bank or non-bank subsidiary of either CCFNB or MBF, and they are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

For CCFNB shareholders, if you have any questions or need assistance in voting your shares, please call Nancy Diehl at (570) 387-7168.

For MBF shareholders, if you have any questions or need assistance in voting your shares, please call Beth Benson at (570) 546-2211.

The accompanying joint proxy statement/prospectus is dated August 17, 2023, and is first being mailed to holders of CCFNB common stock and holders of MBF common stock on or about August 23, 2023.

ADDITIONAL INFORMATION

The accompanying joint proxy statement/prospectus incorporates important business and financial information about CCFNB and MBF from other documents that are not included in or delivered with this document. This information is available to you without charge upon your written or oral request. You can obtain the documents incorporated by reference in this document through the Securities and Exchange Commission website at

http://www.sec.gov. You will also be able to obtain these documents free of charge from CCFNB by accessing CCFNB’s website at https://www.firstcolumbiabank.com or from MBF by accessing MBF’s website at

https://ir.muncybank.com. You may also request these documents in writing, by email or by telephone, at the appropriate address below:

You will not be charged for any of these documents that you request. To obtain timely delivery of these documents, you must request them no later than five (5) business days before the date of the applicable special meeting. This means that holders of CCFNB common stock requesting documents must do so by September 25, 2023, in order to receive them before the CCFNB special meeting, and holders of MBF common stock requesting documents must do so by September 25, 2023, in order to receive them before the MBF special meeting.

No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this document. This document is dated August 17, 2023, and you should assume that the information in this document is accurate only as of such date. You should assume that the information incorporated by reference into this document is accurate as of the date of such incorporated document. Neither the mailing of this document to holders of CCFNB common stock or holders of MBF common stock nor the issuance by CCFNB of shares of CCFNB common stock pursuant to the merger agreement will create any implication to the contrary.

The information on CCFNB’s and MBF’s websites is not part of this document. References to CCFNB’s and MBF’s websites in this document are intended to serve as textual references only.

This document does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Except where the context otherwise indicates, information contained in, or incorporated by reference into, this document regarding CCFNB has been provided by CCFNB, and information contained in, or incorporated by reference into, this document regarding MBF has been provided by MBF.

See “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 199 of the accompanying joint proxy statement/prospectus for further information.

CCFNB Bancorp, Inc.

232 East Street

Bloomsburg, PA 17815

NOTICE OF VIRTUAL SPECIAL MEETING OF CCFNB SHAREHOLDERS

To CCFNB Bancorp, Inc. Shareholders:

On April 17, 2023, CCFNB Bancorp, Inc., or CCFNB, and Muncy Bank Financial, Inc., or MBF, entered into an Agreement and Plan of Merger, as amended, which we refer to as the merger agreement. A copy of the merger agreement is attached as Annex A to the accompanying joint proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting of holders of CCFNB common stock (the “CCFNB special meeting”) will be held virtually via the Internet on October 3, 2023 at 11:00 a.m., Eastern Time. We are pleased to notify you of, and invite you to participate in, the CCFNB virtual special meeting.

At the CCFNB special meeting, you will be asked to vote on the following matters:

CCFNB shareholders may vote on such other business as may properly come before the meeting or at any adjournment thereof. We are not aware of any such other business.

The CCFNB special meeting will be held in a virtual only format conducted via live webcast. As more fully described in the “Questions & Answers” and “The CCFNB Special Meeting” sections of the accompanying joint proxy statement/prospectus, you are entitled to participate in the CCFNB special meeting if, as of the close of business on August 17, 2023, you held shares of CCFNB common stock registered in your name (a “record holder”), or if you held shares through a bank, broker, trustee or other nominee (a “beneficial owner”). Record holders will be able to attend the CCFNB special meeting online, ask questions and vote during the meeting by visiting https://web.lumiagm.com/285477946 and following the instructions. The password for the meeting, if requested, is ccfnb2023. You will need your control number, which can be found on your notice, proxy card or voting instructions form to access the meeting. If you are a beneficial owner, have a valid proxy for the CCFNB

special meeting and register beforehand, you also will be able to attend the CCFNB special meeting online, ask questions and vote during the meeting. See the “Questions and Answers” section of the accompanying joint proxy statement/prospectus for more information for the virtual CCFNB special meeting.

The board of directors of CCFNB has fixed the close of business on August 17, 2023 as the record date for the CCFNB special meeting. Only holders of record of CCFNB common stock as of the close of business on the record date for the CCFNB special meeting are entitled to notice of and to vote at the CCFNB special meeting or any adjournment or postponement thereof.

The CCFNB board of directors unanimously recommends that holders of CCFNB common stock vote “FOR” the CCFNB merger proposal and “FOR” the CCFNB adjournment proposal.

Your vote is important. We cannot complete the transactions contemplated by the merger agreement unless holders of CCFNB common stock approve the CCFNB merger proposal. The affirmative vote, in person or by proxy, of 66- 2/3% of the outstanding shares of CCFNB common stock at the CCFNB special meeting is required to approve the CCFNB merger proposal. Whether or not you plan to attend the CCFNB special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the Internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker or other nominee, please follow the voting instructions on the voting instruction card furnished by such bank, broker or other nominee.

August 17, 2023

Muncy Bank Financial, Inc.

2 N. Main Street

Muncy, Pennsylvania 17756

NOTICE OF VIRTUAL SPECIAL MEETING OF MUNCY BANK FINANCIAL, INC. SHAREHOLDERS

To Muncy Bank Financial, Inc. Shareholders:

On April 17, 2023, Muncy Bank Financial, Inc., or MBF, and CCFNB Bancorp, Inc., or CCFNB, entered into an Agreement and Plan of Merger, as amended, which we refer to as the merger agreement. A copy of the merger agreement is attached as Annex A to the accompanying joint proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting of holders of MBF common stock (the “MBF special

meeting”) will be held virtually via the Internet on October 3, 2023 at 9:30 a.m., Eastern Time. We are pleased to notify you of, and invite you to participate in, the MBF virtual special meeting.

At the MBF special meeting, holders of MBF common stock will be asked to vote on the following matters:

MBF shareholders may vote on such other business as may properly come before the meeting or at any adjournment thereof. We are not aware of any other such business.

The MBF special meeting will be held in a virtual only format conducted via live webcast. As more fully described in the “Questions & Answers” and “The MBF Special Meeting” sections of the accompanying joint proxy statement/prospectus, you are entitled to participate in the MBF special meeting if, as of the close of business on August 17, 2023, you held shares of MBF common stock registered in your name (a “record holder”), or if you held shares through a bank, broker, trustee or other nominee (a “beneficial owner”). Record holders will be able to attend the MBF special meeting online, ask questions and vote during the meeting by visiting www.meetnow.global/MFVNXFL and following the instructions. You will need your control number, which can be found on your notice, proxy or voting instruction form, to access the meeting. If you are a beneficial owner, have a valid proxy for the MBF special meeting and register beforehand, you also will be able to attend the MBF special meeting online, ask questions and vote during the meeting. See the “Questions and Answers” section of the accompanying joint proxy statement/prospectus for more information for the virtual MBF special meeting.

MBF has determined that holders of MBF common stock have the right to dissent with respect to the proposed merger and obtain payment of the fair value of their shares under Chapter 15 of the Pennsylvania Business Corporation Law of 1988, as amended. See “THE MERGER – Appraisal or Dissenters Rights in the Merger” and Annex F in the accompanying joint proxy statement/prospectus.

The MBF board of directors unanimously recommends that holders of MBF common stock vote “FOR” the MBF merger proposal, “FOR” the MBF compensation proposal and “FOR” the MBF adjournment proposal.

Your vote is important. We cannot complete the transactions contemplated by the merger agreement unless the MBF shareholders approve the MBF merger proposal. The affirmative vote of a majority of the votes cast by MFB shareholders, in person or by proxy, at the special meeting is required to approve the MBF merger proposal, the MBF compensation proposal and the MBF adjournment proposal. Whether or not you plan to attend the MBF special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the Internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker or other nominee, please follow the voting instructions on the voting instruction card furnished by such bank, broker or other nominee.

August 17, 2023

TABLE OF CONTENTS

QUESTIONS AND ANSWERS

The following are some questions that you may have about the mergers and the CCFNB special meeting or the MBF special meeting, and brief answers to those questions. We urge you to read carefully the remainder of this joint proxy statement/prospectus because the information in this section does not provide all of the information that might be important to you with respect to the mergers, the CCFNB special meeting or the MBF special meeting. Additional important information is also contained in the documents incorporated by reference into this joint proxy statement/prospectus. See “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 199.

In this joint proxy statement/prospectus, unless the context otherwise requires, when we refer to:

This joint proxy statement/prospectus contains important information about the merger and the other proposals being voted on at the CCFNB and MBF special meetings. This document is also a prospectus that is being delivered to MBF shareholders because, pursuant to the merger agreement, CCFNB is offering shares of CCFNB common stock to MBF shareholders. You should read this document carefully and in its entirety. The enclosed materials allow you to have your shares of common stock voted by proxy without attending your meeting. Your vote is important and we encourage you to submit your proxy as soon as possible.

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Each share of MBF common stock issued and outstanding immediately prior to the effective time of the merger, which we refer to as the effective time, except for shares of MBF common stock owned by MBF, Muncy Bank, CCFNB or FCBT (in each case, other than shares of MBF common stock (i) held in any trust accounts, managed accounts, and the like, or otherwise held in a fiduciary capacity and that are beneficially owned by third parties, or (ii) held by any of them, directly or indirectly, in respect of debts previously contracted), will be converted into the right to receive 0.9259 shares of CCFNB common stock, which we refer to as the exchange ratio, subject to the payment of cash in lieu of fractional shares. The CCFNB shares and cash to be received by MBF shareholders in the merger is referred to as the merger consideration.

After completion of the merger, (i) MBF will cease to exist, and (ii) MBF common stock will cease to be traded and will cease to be quoted on the OTCQB. After the completion of the merger, CCFNB shareholders will continue to own their existing shares of CCFNB common stock. See the information provided in the section entitled “THE MERGER AGREEMENT—Structure of the Merger,” beginning on page 160, and the merger agreement for more information about the merger.

The MBF special meeting will be held virtually via the Internet at www.meetnow.global/MFVNXFL, on October 3, 2023 at 9:30 a.m. Eastern Time.

Even if you plan to attend your respective company’s special meeting virtually, CCFNB and MBF recommend that you vote your shares in advance, as described below, so that your vote will be counted if you later decide not to or become unable to attend the applicable special meeting.

At the MBF special meeting, MBF shareholders will be asked to consider and vote on the following proposals:

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In order to complete the merger, among other things, CCFNB shareholders must approve the CCFNB merger proposal, and MBF shareholders must approve the MBF merger proposal. The approvals of the CCFNB adjournment proposal, the MBF adjournment proposal and the MBF compensation proposal are not conditions to the obligations of CCFNB or MBF to complete the merger.

In this document, the determination date market price means the average of the closing sale prices per share of CCFNB common stock, as reported by OTC Pink, for the price determination period excluding closing sale prices for trading days with less than one hundred (100) shares traded. When we refer to the price determination period in this document, we mean the thirty (30) consecutive trading days immediately preceding the determination date. The determination date refers to the date which is five (5) business days before the date on which all requisite regulatory approvals for the mergers have been received by MBF and CCFNB.

After the completion of the merger, former MBF shareholders will hold approximately 42 percent of the outstanding shares of CCFNB common stock.

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In considering the recommendations of the CCFNB board of directors, CCFNB shareholders should be aware that CCFNB directors and executive officers may have interests in the merger that are different from, or in addition to, the interests of CCFNB shareholders generally. For a more complete description of these interests, see the information provided in the section entitled “THE MERGER—Interests of Certain CCFNB Directors and Executive Officers in the Merger” beginning on page 149.

In considering the recommendations of the MBF board of directors, MBF shareholders should be aware that MBF directors and executive officers may have interests in the merger that are different from, or in addition to, the interests of MBF shareholders generally. For a more complete description of these interests, see the information provided in the section entitled “THE MERGER—Interests of Certain MBF Directors and Executive Officers in the Merger” beginning on page 150.

Each CCFNB shareholder is entitled to cast one (1) vote on each matter properly brought before the CCFNB special meeting for each share of CCFNB common stock that such holder owned of record as of the record date. As of the CCFNB record date, there were 2,080,109 outstanding shares of CCFNB common stock.

Attendance at the special meeting is not required to vote. See below and the section entitled “THE CCFNB SPECIAL MEETING—Proxies”, beginning on page 67, for instructions on how to vote your shares of CCFNB common stock without attending the CCFNB special meeting.

Each MBF shareholder is entitled to cast one (1) vote on each matter properly brought before the MBF special meeting for each share of MBF common stock that such holder owned of record as of the record date. As of the record date, there were 1,608,358 outstanding shares of MBF common stock.

Attendance at the special meeting is not required to vote. See below and the section entitled “THE MBF SPECIAL MEETING—Proxies” beginning on page 73 for instructions on how to vote your shares of MBF common stock without attending the MBF special meeting.

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CCFNB Proposal 2: CCFNB adjournment proposal. Approval of the CCFNB adjournment proposal requires the affirmative vote of a majority of the votes cast by the CCFNB shareholders at the CCFNB special meeting. An abstention, broker non-vote or other failure to vote will have no effect on the outcome of the CCFNB adjournment proposal.

MBF Proposal 2: Compensation proposal. Approval of the compensation proposal requires the affirmative vote of a majority of the votes cast at the MBF special meeting. An abstention, broker non-vote or other failure to vote will have no effect on the outcome of the compensation proposal.

MBF Proposal 3: MBF adjournment proposal. Approval of the MBF adjournment proposal requires the affirmative vote of a majority of the votes cast by the MBF shareholders. An abstention, broker non-vote or other failure to vote will have no effect on the outcome of the MBF adjournment proposal.

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Beneficial Owners. If you hold shares in a brokerage or other account in “street name” as of the record date, you are a “beneficial owner”, and your shares may be voted by you at the CCFNB special meeting or the MBF special meeting, as applicable, as described below. If you choose to vote your shares virtually at the respective special meeting via the applicable special meeting website, you will need the control number, which can be found on your proxy card, notice or voting instruction form, as described below.

CCFNB special meeting.

Record Holders. If you are a record holder of CCFNB common stock, you will be entitled to attend the CCFNB special meeting online, ask questions and vote during the meeting by visiting https://web.lumiagm.com/285477946 and following the instructions. You will need your control number, which can be found on your proxy card, notice or voting instruction form, to access the meeting. The password for the meeting, if requested, is ccfnb2023.

You are a “record owner” if you hold CCFNB common stock directly in your name on the record date.

Beneficial Owners. If you are a beneficial owner of CCFNB common stock, in order to participate in the CCFNB special meeting, you must first obtain a legal proxy from your broker, bank, trustee or other nominee reflecting the number of shares of CCFNB common stock you held as of the record date, your name and email address. You then must submit a request for registration to American Stock Transfer & Trust Company, LLC: (1) by email to proxy@astfinancial.com; (2) by fax to 718-765-8730; or (3) by mail to American Stock Transfer & Trust Company, LLC, Attn: Proxy Tabulation Department, 6201 15^th Avenue, Brooklyn, NY 11219.

Requests for registration must be labeled as “Legal Proxy” and be received by American Stock Transfer & Trust Company, LLC no later than 5:00 p.m. Eastern Time on September 25, 2023.

If you hold shares in a brokerage or other account in “street name” as of the record date, you are a “beneficial owner.”

MBF special meeting.

Record Holders. If you are a record holder of MBF common stock, you will be entitled to attend the MBF special meeting online, ask questions and vote during the meeting by visiting www.meetnow.global/MFVNXFL and following the instructions. You will need your control number, which can be found on your proxy card, notice or voting instruction form, to access the meeting.

You are a “record owner” if you hold MBF common stock directly in your name on the record date.

Beneficial Owners. If you are a beneficial owner of MBF common stock, in order to participate in the MBF special meeting, you must obtain a legal proxy from your bank, broker, trustee or other nominee reflecting the number of shares of MBF common stock you held as of the record date, your name and email address. You then must submit a request for registration to Computershare: (1) by email to legalproxy@computershare.com; (2) by mail to PO Box 43001, Providence, RI 02940-3006. A request for a legal proxy must be received by Computershare at least 3 business days prior to the date of the special meeting.

If you hold shares in a brokerage or other account in “street name” as of the record date, you are a “beneficial owner.”

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Even if you plan to attend the CCFNB special meeting or the MBF special meeting, as applicable, virtually, CCFNB and MBF nevertheless recommend that you vote your shares by proxy in advance as described below so that your vote will be counted if you later decide not to or become unable to attend your company’s special meeting.

Additional information on attending the virtual special meetings can be found under the section entitled “THE CCFNB SPECIAL MEETING—Attending the Virtual Special Meeting” on page 67 and under the section entitled “THE MBF SPECIAL MEETING—Attending the Virtual Special Meeting” on page 73.

If you are a record holder of CCFNB common stock or MBF common stock, you can vote your shares by proxy over the Internet, by telephone or by mail by following the instructions provided in the enclosed proxy card. If you hold shares beneficially in “street name” as a beneficial owner of CCFNB common stock or MBF common stock, you should follow the voting instructions provided by your bank, broker, trustee or other nominee.

Additional information on voting procedures can be found under the section entitled “THE CCFNB SPECIAL MEETING—Attending the Virtual Special Meeting” on page 67 and under the section entitled “THE MBF SPECIAL MEETING—Attending the Virtual Special Meeting” on page 73.

A broker non-vote occurs when a bank, broker, trustee or other nominee is not permitted to vote on a “non-routine” matter without instructions from the beneficial owner of the shares and the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Broker non-votes only

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count toward a quorum if at least one (1) proposal is presented with respect to which the bank, broker, trustee or other nominee has discretionary authority. It is expected that all proposals to be voted on at each of the CCFNB special meeting and the MBF special meeting will be “non-routine” matters, and, as such, we expect that no broker non-votes will be received for either special meeting.

For CCFNB shareholders, failure to instruct your bank, broker, trustee or other nominee on how to vote your CCFNB shares will result in those shares not being voted at the meeting at all. That failure to vote will make it more difficult for CCFNB to achieve a quorum for the CCFNB special meeting and will have the same effect as a vote “AGAINST” the CCFNB merger proposal and will have no effect on the CCFNB adjournment proposal.

For MBF shareholders, failure to instruct your bank, broker, trustee or other nominee on how to vote your MBF shares will result in those shares not being voted at the meeting at all. That failure to vote will make it more difficult for MBF to achieve a quorum for the MBF special meeting but will have no effect on the outcome of the MBF merger proposal, compensation proposal or MBF adjournment proposal.

For purposes of the MBF special meeting, an abstention occurs when an MBF shareholder attends the MBF special meeting and does not vote or returns a proxy with an “abstain” instruction.

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The CCFNB board of directors unanimously recommend that you vote “FOR” the CCFNB merger proposal and the MBF board of directors unanimously recommend that you vote “FOR” the MBF merger proposal. The CCFNB board of directors and the MBF board of directors also unanimously recommend that you vote “FOR” the other proposals to be considered at the CCFNB special meeting and the MBF special meeting, respectively.

If you are a beneficial owner and your shares are held by a bank, broker, trustee or other nominee, you may change your vote by:

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Record Holders. For shares held directly, please complete, sign, date and return each proxy card (or cast your proxy vote by telephone or internet as provided on each proxy card) or otherwise follow the voting instructions provided in this joint proxy statement/prospectus in order to ensure that all of your shares of CCFNB common stock and/or MBF common stock are voted.

Beneficial Owners. For shares held in “street name” through a bank, broker, trustee or other nominee, you should follow the procedures provided by your bank, broker, trustee or other nominee in order to vote your shares.

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D.F. King & Co., Inc.

48 Wall Street, 22^nd Floor

New York, NY 10005

Stockholders may call toll free: (800) 207-3159

Banks and Brokers may call collect: (212) 269-5550

Email: CCFNB@dfking.com

MBF shareholders: If you have any questions about the merger or how to submit your proxy or voting instruction card, or if you need additional copies of this document or the enclosed proxy card or voting instruction card, you should contact Beth Benson, Corporate Secretary of MBF, at the following address: 2 N. Main Street, Muncy, PA 17756, or by telephone at (570) 546-2211.

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SUMMARY

This summary highlights selected information in this joint proxy statement/prospectus and may not contain all of the information that is important to you. You should carefully read this entire joint proxy statement/prospectus and the other documents we refer you to for a more complete understanding of the matters being considered at the CCFNB special meeting and the MBF special meeting.

Information about the Companies (pages 78 and 92)

CCFNB Bancorp, Inc.

CCFNB Bancorp, Inc. is a Pennsylvania corporation and the financial holding company for First Columbia Bank & Trust Co., a Pennsylvania bank and trust company, with its principal place of business in Bloomsburg, Columbia County, Pennsylvania. CCFNB was incorporated June 20, 1983 for the purpose of becoming a bank holding company for Columbia County Farmers National Bank. In 2008, Columbia Financial Corporation, the bank holding company for FCBT, merged with and into CCFNB with CCFNB as the surviving corporation in that holding company merger. Columbia County Farmers National Bank, the bank subsidiary of CCFNB, merged with and into FCBT with FCBT as the surviving bank in the concurrent bank merger. CCFNB is subject to regulation and supervision by the Board of Governors of the Federal Reserve System, which we refer to as the Federal Reserve Board, and by the Pennsylvania Department of Banking and Securities, which we refer to as PADOBS.

As of March 31, 2023, CCFNB had total consolidated assets of approximately $955.0 million, total gross loans not held for sale of approximately $539.3 million, total deposits of approximately $675.4 million and total consolidated stockholders’ equity of approximately $92.6.

CCFNB common stock is quoted on the OTC Pink under the trading symbol “CCFN.”

FCBT is a full-service community commercial bank engaging in a full line of personal, business and municipal financial services and alternative investment products, including corporate and personal fiduciary services. FCBT currently operates 12 full-service banking offices in Columbia, Montour and Northumberland counties in central Pennsylvania. FCBT has 177 employees. FCBT is subject to regulation and supervision by the PADOBS and the Federal Deposit Insurance Corporation, which we refer to as the FDIC.

CCFNB’s principal executive offices are located at 232 East Street, Bloomsburg, PA 17815, its phone number is 570-784-1660 and its website is https://www.firstcolumbiabank.com.

Muncy Bank Financial, Inc.

Muncy Bank Financial, Inc. is a Pennsylvania corporation and the bank holding company for The Muncy Bank and Trust Company, a Pennsylvania bank and trust company with its principal place of business in Muncy, Lycoming County, Pennsylvania. MBF was incorporated on August 25, 1988 for the purpose of becoming the bank holding company for Muncy Bank. MBF is subject to regulation and supervision by the Federal Reserve Board and the PADOBS.

As of March 31, 2023, MBF had total consolidated assets of approximately $650.9 million, total loans of approximately $497.2 million, total deposits of approximately $552.1 million and total consolidated shareholders’ equity of approximately $50.1 million.

MBF common stock is quoted on OTCQB under the trading symbol “MYBF.” Muncy Bank currently operates 10 full-service banking offices located in Lycoming, Clinton and Northumberland counties in central Pennsylvania. Muncy Bank has 127 employees. Muncy Bank is subject to regulation and supervision by the PADOBS and the FDIC.

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MBF’s principal executive offices are located at 2 N. Main Street, Muncy, Pennsylvania 17756, its phone number is (570) 546-2211 and its website is https://ir.muncybank.com.

Recent Developments (page 100)

CCFNB announced second quarter 2023 earnings on August 1, 2023 and MBF announced second quarter earnings on July 31, 2023.

The Merger and the Merger Agreement (pages 113 and 160)

The terms and conditions of the merger are contained in the merger agreement, a copy of which is attached as Annex A to this joint proxy statement/prospectus and incorporated herein by reference. You are encouraged to read the merger agreement carefully and in its entirety, as it is the primary legal document that governs the merger.

Pursuant to the terms and subject to the conditions set forth in the merger agreement, at the effective time of the merger, MBF will merge with and into CCFNB, with CCFNB as the surviving entity. The merger agreement further provides that, immediately following the merger, Muncy Bank will merge with and into FCBT with FCBT as the surviving bank. In connection with the merger, CCFNB will change its name to “Muncy Columbia Financial Corporation” and, in connection with the bank merger, FCBT will change its name to “Journey Bank.” Following the merger, MBF common stock will cease to be quoted on OTCQB and will cease to be publicly traded.

This summary and the copy of the merger agreement attached to this document as Annex A are included solely to provide investors with information regarding the terms of the merger agreement. They are not intended to provide factual information about the parties or any of their respective subsidiaries or affiliates.

Merger Consideration (pages 113 and 160)

Each share of MBF common stock issued and outstanding immediately prior to the effective time, except for certain shares owned by CCFNB or MBF, will be converted into the right to receive 0.9259 shares of CCFNB common stock. MBF shareholders who would otherwise be entitled to receive a fraction of a share of CCFNB common stock in the merger will instead receive, for such fraction, an amount in cash (rounded to the nearest cent) based on the CCFNB determination date market price.

CCFNB common stock is quoted on OTC Pink under the symbol “CCFN,” and MBF common stock is quoted on OTCQB under the symbol “MYBF.” The following table shows the closing sale price of CCFNB common stock and closing bid price of MBF common stock on April 17, 2023, the last trading day before the public announcement of the merger agreement, and on August 15, 2023, the last practicable trading day before the printing of this joint proxy statement/prospectus. This table also shows the implied value of the merger consideration to be issued in exchange for each share of MBF common stock, which was calculated by multiplying such closing sales prices of CCFNB common stock on those dates by the exchange ratio of 0.9259.

For more information on the exchange ratio, see the section entitled “THE MERGER—Terms of the Merger” beginning on page 113 and “THE MERGER AGREEMENT—Merger Consideration” beginning on page 160.

CCFNB’s Reasons for the Merger; Recommendation of CCFNB’s Board of Directors (page 120)

After careful consideration, the CCFNB board of directors, at a special meeting held on April 14, 2023, unanimously (i) determined that the merger agreement and the transactions contemplated thereby, including the

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merger and the issuance of CCFNB common stock, are advisable and fair to and in the best interests of CCFNB and its shareholders and (ii) approved and adopted the merger agreement and the transactions contemplated thereby (including the merger, the issuance of CCFNB common stock, and bank merger agreement). The CCFNB board of directors unanimously recommends that CCFNB shareholders vote “FOR” the CCFNB merger proposal and “FOR” the CCFNB adjournment proposal.

In reaching its decision to approve the merger agreement and the merger and to recommend that CCFNB’s shareholders vote “FOR” the merger agreement and the merger, the CCFNB board of directors evaluated the merger agreement and the merger in consultation with CCFNB management, as well as CCFNB’s financial and legal advisors, and considered a number of factors, including but not limited to the following material factors, which are not presented in any order of priority:

For a more detailed discussion of the CCFNB board of directors’ recommendation and the material factors considered, see “THE MERGER—CCFNB’s Reasons for the Merger; Recommendation of CCFNB’s Board of Directors” beginning on page 120.

Opinion of CCFNB’s Financial Advisor (page 125)

The Kafafian Group, Inc., which we refer to as TKG, acted as financial advisor to CCFNB’s board of directors in connection with the proposed merger and participated in certain of the negotiations leading to the execution of the merger agreement. At the April 14, 2023 meeting at which CCFNB’s board of directors considered the merger and the merger agreement, TKG delivered to the board of directors its oral opinion, which was confirmed in writing dated April 17, 2023, to the effect that, as of April 17, 2023, the merger consideration was fair to CCFNB shareholders from a financial point of view. TKG’s opinion speaks only as of the date of the opinion. The full text of TKG’s opinion is attached as Annex B to this joint proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by TKG in rendering its opinion.

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TKG’s opinion was for the information of, and was directed to, the CCFNB board of directors (in its capacity as such) in connection with its consideration of the financial terms of the merger. The opinion did not address the underlying business decision of CCFNB to engage in the merger or enter into the merger agreement, nor did TKG’s opinion constitute a recommendation to the CCFNB board of directors in connection with the merger. TKG’s opinion does not constitute a recommendation to any holder of CCFNB common stock or any shareholder of any other entity as to how to vote in connection with the merger or any other matter. CCFNB shareholders are urged to read the entire opinion carefully in connection with their consideration of the proposed merger.

For more information, see “THE MERGER—Opinion of CCFNB’s Financial Advisor,” beginning on page 125, and Annex B.

MBF’s Reasons for the Merger; Recommendation of MBF’s Board of Directors (page 134)

After careful consideration, the MBF board of directors, at a meeting held on April 14, 2023, unanimously (i) determined that the merger agreement and the transactions contemplated thereby are advisable and fair to and in the best interests of MBF and its shareholders and (ii) approved and adopted the merger agreement and the bank merger agreement. The MBF board of directors unanimously recommends that MBF shareholders vote “FOR” the MBF merger proposal, “FOR” the compensation proposal and “FOR” the MBF adjournment proposal.

In reaching its decision to approve the merger agreement and the merger and to recommend that MBF’s shareholders vote “FOR” the merger agreement and the merger, the MBF board of directors evaluated the merger agreement and the merger in consultation with MBF management, as well as MBF’s financial and legal advisors, and considered a number of factors, including the following material factors, which are not presented in any order of priority:

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For a more detailed discussion of the MBF board of directors’ recommendation and the material factors considered, see “THE MERGER—MBF’s Reasons for the Merger; Recommendation of MBF’s Board of Directors” beginning on page 134.

Opinion of MBF’s Financial Advisor (page 139)

Griffin Financial Group LLC, which we refer to as Griffin, acted as financial advisor to MBF’s board of directors in connection with the proposed merger and participated in certain of the negotiations leading to the execution of the merger agreement. At the April 14, 2023 meeting at which MBF’s board of directors considered the merger and the merger agreement, Griffin delivered to the board of directors its oral opinion, which was confirmed in writing dated April 14, 2023, to the effect that, as of such date, the merger consideration was fair to the holders of MBF common stock from a financial point of view. Griffin’s opinion speaks only as of the date of the opinion. The full text of Griffin’s opinion is attached as Annex C to this joint proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by Griffin in rendering its opinion.

Griffin’s opinion was for the information of, and was directed to, the MBF board of directors (in its capacity as such) in connection with its consideration of the financial terms of the merger. The opinion did not address the underlying business decision of MBF to engage in the merger or enter into the merger agreement, nor did Griffin’s opinion constitute a recommendation to the MBF board of directors in connection with the merger. Griffin’s opinion does not constitute a recommendation to any holder of MBF common stock or any shareholder of any other entity as to how to vote in connection with the merger or any other matter. MBF shareholders are urged to read the entire opinion carefully in connection with their consideration of the proposed merger.

For more information, see “THE MERGER – Opinion of MBF’s Financial Advisor,” beginning on page 139, and Annex C.

Interests of Certain CCFNB Directors and Named Executive Officers in the Merger (page 149)

In considering the recommendation of CCFNB’s board of directors with respect to the merger, CCFNB’s shareholders should be aware that the directors and named executive officers of CCFNB have certain interests in the merger that may be different from, or in addition to, the interests of CCFNB’s shareholders generally. These interests include, among others, the following:

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CCFNB’s board of directors was aware of these interests and considered them, among other matters, in making its recommendation that CCFNB’s shareholders vote to approve the CCFNB merger proposal. For more information, see “THE MERGER—Background of the Merger” beginning on page 113 and “THE MERGER—CCFNB’s Reasons for the Merger; Recommendation of CCFNB’s Board of Directors” beginning on page 120. These interests are described in more detail below, and certain of them are quantified in the narrative and in the section entitled “THE MERGER—Interests of Certain CCFNB Directors and Named Executive Officers in the Merger” beginning on page 149.

Interests of Certain MBF Directors and Named Executive Officers in the Merger (page 150)

In considering the recommendations of MBF’s board of directors, MBF’s shareholders should be aware that MBF’s directors and named executive officers have interests in the merger that may be different from, or in addition to, the interests of the MBF’s shareholders generally. These interests include, among others, the following:

MBF’s board of directors was aware of these interests, including the material terms thereof, and considered them, among other matters, in making its recommendation that MBF’s shareholders vote to approve the MBF merger proposal. For more information, see “THE MERGER—Background of the Merger” beginning on page 113 and “THE MERGER—MBF’s Reasons for the Merger; Recommendation of MBF’s Board of Directors” beginning on page 134. These interests are described in more detail, and certain of them are quantified, in the section entitled “THE MERGER—Interests of Certain MBF Directors and Named Executive Officers in the Merger” beginning on page 150.

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Governance of CCFNB After the Merger (page 153)

Boards of Directors of the Combined Company and the Combined Bank

At the effective time of the merger, the number of directors that will comprise the full boards of directors of CCFNB and FCBT will be twenty, of which (i) twelve will be all of the existing directors of CCFNB immediately prior to the effective time and (ii) eight will be all of the existing directors of MBF immediately prior to the effective time. Four of the CCFNB directors and two of the MBF directors, however, have agreed, pursuant to the terms of their respective voting agreements, to resign from the boards of directors of CCFNB and FCBT effective as of the three month anniversary of the effective time of the mergers. As a result, the boards of directors of CCFNB and FCBT will thereafter be comprised of fourteen directors, eight of whom will be directors of CCFNB prior to the effective time, referred to in this document as the CCFNB continuing directors, and six of whom will be directors of MFB prior to the effective time, referred to in this document as the MBF continuing directors.

CCFNB has a classified board of directors consisting of three classes. Each director generally holds office for a three-year term. The terms of the classes are staggered so that the term of office of one class expires each year. The eight MBF directors will be appointed among the three classes so that the numbers of directors in each class, both as of the effective time of the merger and after the resignation of directors to be effective upon the three month anniversary of the effective time, will be as nearly equal as possible.

CCFNB has agreed, pursuant to the merger agreement, to renominate each MBF continuing director to one additional term when the initial term of the class to which he or she is appointed expires. In addition, any vacancies in MBF continuing directors occurring during the initial term or the first additional term of the class affected by the vacancy will be generally nominated by the remaining MBF continuing directors.

CCFNB also has agreed that after completion of the merger, non-employee directors fees will be as follows: (i) $1,550 per month retainer fee; (ii) $700 per month board fee; (iii) $350 per committee meeting fee; (iv) $450 per special meeting fee; and (v) $600 per meeting committee chair fee in lieu of the standard committee meeting fee.

Lance O. Diehl, currently President and Chief Executive Officer of CCFNB and FCBT, will become Chairman, President and Chief Executive Officer of CCFNB and Executive Chairman of FCBT upon the effective time of the mergers. Robert J. Glunk, currently Chairman, President and Chief Executive Officer of MBF and Muncy Bank, will become Senior Executive Vice President and Chief Operating Officer of CCFNB and President and Chief Executive Officer of FCBT upon the effective time of the mergers.

Mr. Diehl’s amended and restated employment agreement dated August 2, 2023 with CCFNB and FCBT provides for a term expiring March 31, 2026, at which time it is anticipated that Mr. Diehl would retire from active service as an executive officer of CCFNB and FCBT and Mr. Glunk would succeed Mr. Diehl as chief executive officer of CCFNB. In order to facilitate both a successful integration of CCFNB and MBF upon completion of the merger and an orderly succession transition, Mr. Diehl’s employment agreement further provides that no later than 12 months after the effective date of the merger, but not earlier than 4 months after such effective date, Mr. Diehl, at his election or the election of the CCFNB board of directors, will fulfill his duties as Chairman, President and Chief Executive Officer of CCFNB and Executive Chairman of FCBT on a part-time basis consisting of not less than 3 days per week, or 24 hours per week, and that Mr. Diehl shall make himself available as may be necessary or appropriate to fulfill such duties and responsibilities.

At the effective time, FCBT will establish an Advisory Board of Directors and will appoint to it, for a three year term, each director of CCFNB and FCBT and each director of MBF and Muncy Bank who retires from the CCFNB and Muncy Bank boards of directors, effective as of the three month anniversary of the effective time of the mergers. Advisory Board members will receive an annual fee in the amount of $25,000 for their service.

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At the effective time, the other key officers of CCFNB and FCBT will be as set forth below:

Other CCFNB Key Officers

Other FCBT Key Officers

Name and Headquarters (page 155)

The merger agreement provides that the names of the surviving corporation and surviving bank will be Muncy Columbia Financial Corporation and Journey Bank, respectively, and that the headquarters and main offices of Muncy Columbia Financial Corporation and Journey Bank will remain located at 232 East Street, Bloomsburg, Pennsylvania.

Regulatory Approvals (page 155)

Subject to the terms of the merger agreement, CCFNB and MBF have agreed to cooperate with each other and use reasonable best efforts to promptly prepare and file all necessary documentation to effect all applications, notices, petitions and filings, to make such filings as promptly as possible, to obtain as promptly as practicable all permits, consents, approvals and authorizations of all third parties and governmental entities which are necessary or advisable to consummate the transactions contemplated by the merger agreement (including the merger and the bank merger), and to comply with the terms and conditions of all such permits, consents, approvals and authorizations of all such governmental entities. The requisite regulatory approvals include, among others, the Federal Reserve Board, for the merger, the approval of the FDIC for the bank merger, and the approval of the PADOBS for the merger and the bank merger. As of the date of this joint proxy statement/prospectus, CCFNB has received notice of the approval of the bank merger by the FDIC, the approval of the merger and the bank merger by the PADOBS and the granting by the Federal Reserve Board of CCFNB’s request for a waiver, in accordance with applicable regulations, of the requirement to apply for approval of the merger.

Expected Timing of the Merger

Neither CCFNB nor MBF can predict the actual date on which the merger will be completed, or if the merger will be completed at all, because completion is subject to conditions and factors outside the control of both companies. MBF must first obtain the approval of MBF shareholders for the MBF merger proposal, and CCFNB must first obtain the approval of CCFNB shareholders for the CCFNB merger proposal. CCFNB and MBF must also satisfy certain other closing conditions. CCFNB and MBF expect the merger to be completed promptly once CCFNB and MBF have obtained their respective shareholders’ approvals noted above and have satisfied the other closing conditions. Subject to the foregoing, CCFNB and MBF anticipate that the mergers will be completed during the fourth quarter of 2023.

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Conditions to Complete the Merger (page 173)

As more fully described in this joint proxy statement/prospectus and in the merger agreement, the completion of the merger depends on a number of conditions being satisfied or, where legally permissible, waived. These conditions include:

Termination of the Merger Agreement (page 174)

The merger agreement can be terminated at any time prior to completion of the merger, whether before or after the receipt of the requisite MBF vote, in the following circumstances:

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Termination Fee (page 176)

If the merger agreement is terminated under certain circumstances, including circumstances involving an alternative acquisition proposal or recommendation change, CCFNB or MBF may be required to pay a termination fee to the other equal to $2.6 million.

Accounting Treatment (page 155)

The merger will be accounted for as an acquisition of MBF by CCFNB under the acquisition method of accounting in accordance with accounting principles generally accepted in the United States, or GAAP.

The Rights of MBF Shareholders Will Change as a Result of the Merger (page 184)

The rights of MBF shareholders are governed by Pennsylvania law and the MBF articles of incorporation and bylaws. In the merger, MBF shareholders will become CCFNB shareholders, and their rights will be governed by Pennsylvania law and the CCFNB articles of incorporation and bylaws. MBF shareholders will have different rights once they become CCFNB shareholders due to differences between the MBF governing documents, on the one hand, and the CCFNB governing documents, on the other hand. These differences are described in more detail under the section entitled “COMPARISON OF THE RIGHTS OF CCFNB SHAREHOLDERS AND MBF SHAREHOLDERS” beginning on page 184.

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Quotation of CCFNB Common Stock; Cessation of Quotation of MBF Common Stock (page 35)

The shares of CCFNB common stock to be issued in the merger are quoted on OTC Pink. Following the merger, shares of CCFNB common stock will continue to be traded on OTC Pink. The OTC Pink trading market lacks the depth, liquidity and orderliness to maintain a liquid market. Following completion of the merger, CCFNB intends to register the CCFNB common stock under the Securities Exchange Act of 1934, as amended, and to file annual, quarterly and current reports and proxy statements with the SEC. It is expected that this enhanced reporting by CCFNB will provide greater liquidity and a deeper market in which to buy or sell shares of CCFNB common stock and enable the CCFNB board of directors to consider listing CCFNB shares on a major stock exchange at a later time,

Following completion of the merger, MBF common stock will cease to be traded and cease to be quoted on OTCQB.

The CCFNB Special Meeting (page 65)

The CCFNB special meeting will be held virtually via the Internet on October 3, 2023 at 11:00 a.m., Eastern Time.

At the CCFNB special meeting, CCFNB shareholders will be asked to vote on the following matters:

You may vote at the CCFNB special meeting if you owned shares of CCFNB common stock at the close of business on August 17, 2023. As of August 17, 2023, there were 2,080,109 shares of CCFNB common stock outstanding.

As of the close of business on July 31, 2023, CCFNB’s directors and executive officers were entitled to vote an aggregate of 142,661 shares of CCFNB common stock at the special meeting, which represents approximately

6.86% of the issued and outstanding shares of CCFNB common stock entitled to vote at the special meeting.

Each director and executive officer of CCFNB, solely in such director’s or executive officer’s capacity as a shareholder of CCFNB, has entered into a voting agreement with CCFNB and MBF requiring each of them to vote all shares of CCFNB or MBF common stock owned by such director and over which they have sole voting power in favor of the CCFNB merger proposal and the MBF merger proposal, respectively.

The CCFNB merger proposal will be approved if at least 66-2/3% of the outstanding shares of CCFNB common stock are voted “FOR” such proposal. If a CCFNB shareholder present at the CCFNB special meeting abstains from voting, or responds by proxy with an “ABSTAIN,” it will have the same effect as a vote “AGAINST” such proposal. If a CCFNB shareholder is not present at the CCFNB special meeting and does not respond by proxy or does not provide his, her or its bank, broker, trustee or other nominee with instructions, as applicable and as may be required, it will have the same effect as a vote “AGAINST” such proposal.

The CCFNB adjournment proposal will be approved if a majority of the votes cast by the CCFNB shareholders at the CCFNB special meeting are voted “FOR” such proposal. An abstention or failure to vote at all will have no effect on the outcome of the CCFNB adjournment proposal.

The MBF Special Meeting (page 71)

The MBF special meeting will be held virtually via the Internet on October 3, 2023 at 9:30 a.m., Eastern Time. At the MBF special meeting, MBF shareholders will be asked to vote on the following matters:

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You may vote at the MBF special meeting if you owned shares of MBF common stock at the close of business on August 17, 2023. As of August 17, 2023, there were 1,608,358 shares of MBF common stock outstanding.

As of August 17, 2023, MBF directors and executive officers were entitled to vote an aggregate of 171,652 shares of MBF common stock at the special meeting, which represents approximately 10.67% of the issued and outstanding shares of MBF common stock entitled to vote at the special meeting.

Each director and executive officer of MBF, solely in such director’s or executive officer’s capacity as a shareholder of MBF, has entered into voting agreement with CCFNB and MBF requiring each of them to vote all shares of MBF and CCFNB common stock owned by such director or executive officer and over which he or she has sole voting control in favor of the MBF merger proposal and the CCFNB merger proposal, respectively.

The MBF merger proposal will be approved if a majority of the votes cast by the holders of outstanding shares of MBF common stock entitled to vote at the special meeting are voted “FOR” such proposal. If an MBF shareholder abstains from voting or fails to vote at all, it will have no effect on the outcome of such proposal.

The MBF compensation proposal will be approved if a majority of the votes cast by the holders of outstanding shares of MBF common stock at the MBF special meeting are voted in favor of such proposal. If an MBF shareholder present at the MBF special meeting abstains from voting or fails to vote at all, it will have no effect on the outcome of the compensation proposal.

The MBF adjournment proposal will be approved if a majority of the votes cast by the holders of outstanding shares of MBF common stock at the MBF special meeting are voted in favor of such proposal. If an MBF shareholder abstains from voting or fails to vote at all, it will have no effect on the outcome of such proposal.

Appraisal or Dissenters’ Rights in the Merger (page 157)

MBF shareholders will have the right under Pennsylvania law to dissent with respect to the proposed merger and to obtain payment of the fair value of their shares in cash as determined by an appraisal process in accordance with the procedures under Subchapter D of Chapter 15 of the Pennsylvania Business Corporation Law of 1988, as amended (the “PBCL”). CCFNB shareholders will not have dissenters’ or appraisal rights. The statutorily determined “fair value” could be more or less than the value of the merger consideration. MBF shareholders who intend to exercise dissenters’ rights should read the statute carefully and consult with their own legal counsel. Failure to strictly comply with the procedures set forth in the PBCL will result in the loss of dissenters’ rights. Also, if you exercise dissenters’ rights, you may have taxable income as a result, so you should consult with your own tax advisor if you intend to dissent. For more information, see “THE MERGER—Appraisal or Dissenters’ Rights in the Merger” beginning on page 157 and Annex F.

Material U.S. Federal Income Tax Consequences of the Merger (page 178)

The merger is intended to qualify as a “reorganization” within the meaning of Section 368(a) of the Code and it is a condition to the respective obligations of CCFNB and MBF to complete the merger that each of CCFNB and MBF receives a legal opinion to that effect. Accordingly, assuming the receipt and accuracy of these opinions, a holder who receives solely shares of CCFNB common stock (or receives CCFNB common stock and cash solely in lieu of a fractional share) in exchange for shares of MBF common stock in the merger generally will not recognize any gain or loss upon the merger, except with respect to the cash received in lieu of a fractional share of CCFNB common stock. You should be aware that the tax consequences of the merger may depend upon your own particular tax situation. In addition, you may be subject to state, local or foreign tax laws that are not discussed in this joint proxy statement/prospectus. You should therefore consult with your own tax advisor for a full understanding of the tax consequences of the merger to you.

For more detailed information, please refer to “MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES OF THE MERGER” beginning on page 178.

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The United States federal income tax consequences described above may not apply to all MBF shareholders. Your tax consequences will depend on your individual situation. Accordingly, we strongly urge you to consult your tax advisor for a full understanding of the particular tax consequences of the merger to you.

Risk Factors (page 46)

Consummation of the merger and ownership of CCFNB common stock following the merger are subject to certain risks, including risks relating to the financial services industry generally, and CCFNB’s business. In evaluating the merger agreement, the merger or the issuance of shares of CCFNB common stock, you should carefully read this joint proxy statement/prospectus and give special consideration to the factors discussed in the section entitled “RISK FACTORS” beginning on page 46, including, but not limited to, the following:

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Some of the statements contained or incorporated by reference into this joint proxy statement/prospectus are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, Section 27A of the Securities Act, and Section 21E of the Exchange Act. Any statement that does not describe historical or current facts is a forward-looking statement, including statements with respect to CCFNB’s and MBF’s beliefs, goals, intentions and expectations regarding the proposed transaction, revenues, earnings, loan production, asset quality and capital levels, among other matters; our estimates of future costs and benefits of the actions we may take; our assessments of probable losses on loans; our assessments of interest rate and other market risks; our ability to achieve our financial and other strategic goals; the expected timing of completion of the proposed transaction; the expected cost savings, synergies and other anticipated benefits from the proposed transaction; and other statements that are not historical facts.

Forward-looking statements are typically identified by words such as “believe,” “expect,” “anticipate,” “project,” “intend,” “target,” “estimate,” “continue,” “positions,” “prospects” or “potential,” by future conditional verbs such as “will,” “would,” “should,” “could,” or “may,” or by variations of such words or by similar expressions. Forward-looking statements are based on current expectations, estimates and projections about CCFNB’s and MBF’s businesses, beliefs of CCFNB’s and MBF’s management and assumptions made by CCFNB’s and MBF’s management. These statements are not guarantees of future performance and are subject to numerous risks, uncertainties and assumptions that are difficult to predict, change over time, and many of which are beyond the control of CCFNB and MBF. Therefore, actual outcomes and results may differ materially from what is expressed or forecasted in such forward-looking statements.

In addition to the factors discussed in the section entitled “RISK FACTORS” beginning on page 46, forward-looking statements contained in this proxy statement/prospectus are subject to, among others, the following risk, uncertainties, and assumptions:

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The foregoing factors are representative of the future factors that could affect the outcome of the forward-looking statements. In addition, such statements could be affected by general industry and market conditions and growth rates, general economic and political conditions, either nationally or in the central Pennsylvania communities in which CCFNB, MBF or their respective subsidiaries do business, including interest rate and currency exchange rate fluctuations, changes and trends in the securities markets, and other future factors.

For any forward-looking statements made in this joint proxy statement/prospectus or in any documents incorporated by reference into this joint proxy statement/prospectus, CCFNB and MBF claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995, Section 27A of the Securities Act, and Section 21E of the Exchange Act. You are cautioned not to place undue reliance on the forward-looking statements, which speak only as of the date of this joint proxy statement/prospectus or the dates of the documents incorporated by reference in this joint proxy statement/prospectus. Annualized, pro forma, projected and estimated numbers are used for illustrative purposes only, are not forecasts and may not reflect actual results. Except as required by applicable law, neither CCFNB nor MBF undertakes to update these forward-looking statements to reflect facts, circumstances, assumptions or events that occur after the date the forward-looking statements are made.

CCFNB and MBF expressly qualify, in their entirety, all forward-looking statements attributable to either of them or any person acting on their behalf by the cautionary statements contained or referred to in this joint proxy statement/prospectus.

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SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA OF CCFNB BANCORP, INC.

Set forth below are highlights from CCFNB’s consolidated financial data as of and for the years ended December 31, 2022 and 2021 and as of and for the three months ended March 31, 2023 and 2022. The results of operations for the three months ended March 31, 2023 and 2022 are not necessarily indicative of the results of operations for the full year or any other interim period. CCFNB management prepared the unaudited information on the same basis as it prepared CCFNB’s audited consolidated financial statements. In the opinion of CCFNB management, this information reflects all adjustments, consisting of only normal recurring adjustments, necessary for a fair presentation of this data for those dates. You should read this information in conjunction with CCFNB’s consolidated financial statements, which are included herein. See Index to Financial Statements on page F-1.

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SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA OF MUNCY BANK FINANCIAL, INC.

The following table presents MBF’s selected consolidated financial data. The balance sheet and income state data for the years ended December 31, 2022 and 2021 are derived from MBF’s audited financial statements for the periods then ended. The results of operations for the three months ended March 31, 2023 and 2022 are not necessarily indicative of the results of operations for the full year or any other interim period. MBF management prepared the unaudited information on the same basis as it prepared MBF’s audited consolidated financial statements. In the opinion of MBF management, this information reflects all adjustments, consisting of only normal recurring adjustments, necessary for a fair presentation of this data for those dates. You should read this information in conjunction with MBF’s consolidated financial statements, which are included herein. See Index to Financial Statements on Page F-1.

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COMPARATIVE PER SHARE DATA

The following table sets forth certain historical and pro forma combined per share data for each of CCFNB and MBF. The pro forma data gives effect to the merger and is derived from the CCFNB unaudited pro forma combined per share data included in this proxy statement/prospectus.

This data should be read together with the selected historical financial data of CCFNB and MBF included in this proxy statement/prospectus. The per share data is not necessarily indicative of the operating results that CCFNB would have achieved had it completed the merger as of the beginning of the periods presented and should not be considered as representative of future operations. The pro forma combined information set forth below was determined based upon the issuance of an aggregate of 1,489,179 shares by CCFNB. This number of shares represents the assumed conversion of the outstanding shares of MBF common stock as of March 31, 2023 to shares of CCFNB common stock.

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COMPARATIVE MARKET PRICE DATA AND DIVIDEND INFORMATION

Neither CCFNB common stock nor MBF common stock is listed on an exchange. CCFNB common stock is quoted on OTC pink under the symbol “CCFN.” MBF common stock is quoted on OTCQB under the symbol “MYBF.” Although CCFNB common stock and MBF common stock are quoted on OTC Pink and OTCQB, respectively, these trading markets lack the depth, liquidity, and orderliness to maintain a liquid market. The OTC Pink and OTCQB prices are quotations, which reflect inter-dealer prices, without retail mark-up, markdown or commissions and may not represent actual transactions.

The holders of CCFNB and MBF common stock receive dividends as and when declared by CCFNB’s or MBF’s board of directors, as the case may be. Following the completion of the merger, subject to approval and declaration by CCFNB’s board of directors, CCFNB expects to pay quarterly cash dividends in an amount equal to or greater than a rate of $1.67 per share per year. However, the payment of dividends by CCFNB is subject to numerous factors, and no assurance can be given that CCFNB will pay dividends following the completion of the merger or that dividends will not be reduced in the future. See the section of this joint proxy statement/prospectus entitled “RISK FACTORS,” beginning on page 46, and “SUPERVISION AND REGULATION-Payment of Dividends and Other Restrictions” on page 104 for a discussion of restrictions on CCFNB’s ability to pay dividends.

The following table sets forth the high and low sales prices of shares of CCFNB and MBF’s common stock and the quarterly cash dividends declared per share for the periods indicated.

On April 17, 2023, the last full trading day before the public announcement of the merger agreement, the closing price of shares of CCFNB common stock as reported on OTC Pink was $40.05. On August 15, 2023, the last practicable trading day before the printing date of this proxy statement/prospectus, the closing price of shares of CCFNB common stock as reported on OTC Pink was $40.50.

MBF shareholders are advised to obtain current market quotations for CCFNB common stock. The market price of CCFNB common stock will fluctuate between the date of this proxy statement/prospectus and the completion of the merger. No assurance can be given concerning the market price of CCFNB common stock before or after the effective date of the merger.

Under CCFNB’s treasury stock repurchase program, CCFNB is currently authorized to repurchase up to 135,300 shares of its common stock, or 6.5% of its issued and outstanding shares as of March 31, 2023. As permitted by securities laws and other legal requirements and subject to market conditions and other factors, purchases may be made from time to time in the open market at prevailing prices, or through privately negotiated transactions. In 2022, CCFNB purchased 500 shares of its common stock in the open market pursuant to the plan at an average price of $50.00 per share, and did not purchase any shares in the first quarter of 2023.

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SUMMARY SELECTED PRO FORMA CONDENSED COMBINED DATA

The following table shows selected financial information on a pro forma combined basis giving effect to the merger (which is known as “pro forma” information) as if the merger had become effective as of the date presented, in the case of the balance sheet information, and at the beginning of the period presented, in the case of the income statement information. The pro forma information reflects the acquisition method of accounting.

CCFNB anticipates that the Merger will provide the combined company with financial benefits that include reduced operating expenses and greater revenue. The pro forma information, while helpful in illustrating the financial characteristics of the combine company following the merger under one set of assumptions, does not reflect the benefit from reduced operating expenses or greater revenue and, accordingly, does not attempt to predict or suggest future results. The pro forma information also does not necessarily reflect what the historical results of CCFNB would have been had the CCFNB and MBF been combined during these periods.

The Conversion Ratio of 0.9259 was used in preparing this selected pro forma information. You should read this summary pro forma information in conjunction with the information under “Unaudited Pro Forma Condensed Combined Consolidated Financial Information relating to the Merger” and with the historical information in this document on which it is based.

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UNAUDITED PRO FORMA CONDENSED COMBINED CONSOLIDATED FINANCIAL INFORMATION RELATING TO THE MERGER

The following unaudited pro forma condensed consolidated combined financial information and explanatory notes show the historical financial positions and results of operations of CCFNB and MBF, and have been prepared to illustrate the effects of the merger under the acquisition method of accounting, with CCFNB treated as the acquirer. The unaudited pro forma condensed combined consolidated balance sheet as of March 31, 2023 gives effect to the merger as if the transaction had occurred on March 31, 2023. The unaudited pro forma condensed combined income statements for the three months ended March 31, 2023 and year ended December 31, 2022, give effect to the merger as if the transaction had become effective beginning on the first day of the fiscal years presented. Certain reclassifications have been made to MBF’s historical financial information in order to conform to CCFNB’s presentation of financial information.

The unaudited pro forma condensed combined consolidated financial information is presented for illustrative purposes only and is not necessarily indicative of the results of operations or financial condition had the merger been completed on the dates described above, nor is it necessarily indicative of the results of operations in future periods or the future financial position of the combined entities.

The pro forma financial information includes estimated adjustments, including adjustments to record assets and liabilities of MBF at their fair value, and represents the pro forma estimates by CCFNB, based on available fair value information. The adjustments included in this unaudited pro forma condensed combined financial information are preliminary and may be revised. The pro forma information also does not reflect the benefits of expected cost savings or any potential impacts of potential revenue enhancements and, accordingly, does not attempt to predict or suggest future results. It also does not necessarily reflect what the historical results of the combined company would have been had the companies been combined during these periods.

The actual value of CCFNB common shares to be recorded as consideration in the merger will be based on the closing price of CCFNB’s common shares at the effective date of the merger. The proposed merger is expected to be completed in the fourth quarter of 2023, but there can be no assurance that the merger will be completed as anticipated. For purposes of the pro forma financial information, the fair value of CCFNB’s common shares to be issued in connection with the merger was based on CCFNB’s closing price of $40.00 as of May 25, 2023. The merger expenses will be funded with cash.

The pro forma adjustments included herein are subject to change depending on changes in interest rates, credit conditions and the components of assets and liabilities, and as additional information becomes available and additional analyses are performed. The final allocation of the purchase price for the merger will be determined after it is completed and after completion of thorough analyses to determine the fair value of MBF’s tangible and identifiable intangible assets and liabilities as of the effective date of the merger. Increases or decreases in the estimated fair values of the net assets as compared with the information shown in the unaudited pro forma condensed combined consolidated financial information may change the amount of the purchase price allocated to goodwill and other assets and liabilities and may impact CCFNB’s statement of income due to adjustments in yield and/or amortization of the adjusted assets or liabilities. Any changes to MBF’s shareholders’ equity, including results of operations from March 31, 2023, through the date the merger is completed, will also change the purchase price allocation, which may include the recording of a lower or higher amount of goodwill. The final adjustments may be materially different from the unaudited pro forma adjustments presented herein.

CCFNB anticipates that the merger will provide the combined company with financial benefits that include reduced operating expenses. The combined company expects to realize cost savings of the anticipated non-interest expense of the combined CCFNB and MBF. These cost savings are not included in these pro forma statements and there can be no assurance that estimated cost savings will be realized.

In June 2016 and through several amendments, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-13, “Financial Instruments – Credit Losses (Topic 326):

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Measurement of Credit Losses on Financial Instruments,” (collectively referred to as “ASC 326”). ASC 326 introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. It modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. It also modifies the measurement principles for modifications of loans to borrowers experiencing financial difficulty, including how the allowance for credit losses is measured for such loans. CCFNB and MBF both adopted ASC 326 effective January 1, 2023. The pro forma analysis includes identification of Purchase Credit Deteriorated (“PCD”) loans and non-PCD loans and the estimated CECL allowances for the acquired MBF loans in accordance with ASC 326.

The unaudited pro forma condensed combined financial information is provided for illustrative information purposes only. The unaudited pro forma condensed combined financial information is not necessarily, and should not be assumed to be, an indication of the actual results that would have been achieved had the merger been completed as of the dates indicated or that may be achieved in the future. The unaudited pro forma condensed combined consolidated financial information should be read in conjunction with (i) the accompanying Notes to Unaudited Pro Forma Condensed Combined Consolidated Financial Information; (ii) CCFNB’s and MBF’s unaudited historical consolidated financial statements as of and for the three months ended March 31, 2023 and, (iii) CCFNB’s and MBF’s audited historical consolidated financial statements and accompanying notes as of and for the year ended December 31, 2022. See “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 199 of this joint proxy statement/prospectus.

The unaudited pro forma shareholders’ equity and net income are qualified by the statements set forth under this caption and should not be considered indicative of the market value of CCFNB’s common shares or the actual or future results of operations of CCFNB for any period. Actual results may be materially different than the pro forma information presented.

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