X0609 4 2026-09-16 0001849867 Catalyst Bancorp, Inc. CLST 0001885818 Kleiser Kirk E. false C/O CATALYST BANCORP INC 235 N COURT ST OPELOUSAS LA 70570 true false false false 0 Common Stock 2026-09-16 4 M 0 529 12.08 A 45887 D Common Stock 2026-09-16 4 M 0 16928 13.30 A 45358 D Common Stock 20099 I By IRA Common Stock 4100 I By Spouse in IRA Common Stock 900 I By Spouse Stock Option (Right to Buy) 13.30 2026-09-16 4 M 0 16928 0 D 2032-09-01 Common Stock 16928 4232 D Stock Option (Right to Buy) 12.08 2026-09-16 4 M 0 529 0 D 2035-06-10 Common Stock 529 2116 D Stock Option (Right to Buy) 15.96 2036-06-10 Common Stock 2645 2645 D The options are vesting at a rate of 20% per year commenced on June 10, 2026. As of the date of this filing 529 options were exercised. Includes 1,058 shares granted 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 847 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 1,058 shares that commenced vesting 20% per year on June 10, 2026. Includes 1,696 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 8,464 shares that commenced vesting 20% per year on September 1, 2023. The options are vesting at a rate of 20% per year commenced on September 1, 2023. As of the date of this filing 16,928 options were exercised. The options vest at a rate of 20% per year commencing on June 10, 2027. /s/ Jutta Codori by P.O.A. for Kirk E. Kleiser 2026-09-18