Form 3 Filing for Matthew K. Durkee

This filing details the ownership of securities by Matthew K. Durkee, who holds the positions of President of Commercial Banking and SVP, Chief Banking Officer at Community Financial System, Inc. (CBU). The report indicates direct ownership of 3,257 shares of Common Stock. Additionally, Durkee has indirect ownership of 9,620.2561 shares of Common Stock through his participation in the company's 401(k) Plan. The filing also discloses the grant of stock options, with specific vesting schedules and exercise prices. These options include 2,496 shares vesting on March 14, 2028, with an exercise price of $54.06; 5,451 shares vesting on March 19, 2029, with an exercise price of $44.27; and 4,474 shares vesting on March 18, 2030, with an exercise price of $58.10. The report was signed on February 23, 2026.