X0508 4 2026-02-03 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001201821 STICKELS ERIC C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Common Stock 2026-02-03 4 S 0 2000 64.746 D 33342 D Common Stock 14907.6568 I By Wife's Community Financial System, Inc. 401(k) The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $64.60 to $64.805, inclusive. The reporting person undertakes to provide Community Financial System, Inc., any security holder of Community Financial System, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. Danielle M. Cima, pursuant to a Confirming Statement executed by Eric E. Stickels 2026-02-05