X0609 4 2026-09-01 0001849867 Catalyst Bancorp, Inc. CLST 0001911094 Bourque Jacques L.J. false C/O CATALYST BANCORP INC 235 N COURT ST OPELOUSAS LA 70570 false true false false CHIEF FINANCIAL OFFICER 0 Common Stock 2026-09-01 4 F 0 131 17.81 D 4335 D Common Stock 860.6112 I By 401(k) Plan Common Stock 2793.2688 I By ESOP Common Stock 100 I As Utma Custodian for Quinn Bourque Common Stock 100 I As Utma Custodian for Levi Bourque Stock Option (Right to Buy) 13.30 2032-09-01 Common Stock 5000 5000 D Stock Option (Right to Buy) 12.08 2035-06-10 Common Stock 4000 4000 D Stock Option (Right to Buy) 15.96 2036-06-10 Common Stock 2000 2000 D Disposition solely to meet tax obligation for distribution from stock benefit plan. Includes 1,600 shares granted pursuant to the Issuer's 2022 Recognition and Retention Plan and Trust Agreement that reflect the unvested portion of a grant amount originally covering 2,000 shares that commenced vesting 20% per year on June 10, 2026. Includes 400 shares granted pursuant to the Issuer's 2022 Recognition and Retention Plan and Trust Agreement that reflect the unvested portion of a grant amount originally covering 2,000 shares that commenced vesting 20% per year on September 1, 2023. Represents the grant of shares pursuant to the Issuer's 2022 Recognition and Retention Plan and Trust Agreement that vest at 20% per year commencing on June 10, 2027. Includes shares acquired in the Catalyst Bank 401(k) Plan since the last filed Form 4, based on a report dated August 27, 2026. Includes shares allocated to the reporting person's account in the ESOP since the last filed Form 4, as of December 31, 2025. These options are vesting at a rate of 20% per year that commenced on September 1, 2023. These options are vesting at a rate of 20% per year that commenced on June 10, 2026. The options vest at a rate of 20% per year commencing on June 10, 2027. /s/ Jutta Codori by P.O.A. for Jacques L. J. Bourque 2026-09-02