Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

June 23, 2023

We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 333-119887, 333-119590, 333-185556, 333-266241, and 333-221190) of Community Bank System, Inc. of our report dated June 23, 2023, appearing in the Annual Report on Form 11-K of the Community Bank System, Inc. 401(k) Employee Stock Ownership Plan for the year ended December 31, 2022.

/s/ Dannible & McKee, LLP

Dannible & McKee, LLP

Syracuse, New York