Confirming Statement

This Confirming Statement (?Statement?) confirms that the undersigned,
Joseph F. Serbun, has authorized, directed and designated each of
Danielle M. Cima, George J. Getman and Marguerite K. Geiss (each a
?Designee? and together, the ?Designees?), or either of them acting
singly, to: (1) prepare, execute and file for and on behalf of the undersigned
with the U.S. Securities and Exchange Commission (the ?SEC?) a Form
ID, including amendments thereto, enabling the undersigned to make
electronic filings with the SEC of reports required by Section 16(a) of
the Securities Exchange Act of 1934 and any rule or regulation
thereunder; and (2) prepare, execute and file for and on behalf of the
undersigned with the SEC and any stock exchange or similar authority,
all Forms 3, 4, and 5, including any amendments thereto, that the undersigned
is required to file as an officer and/or director of Community Bank System,
Inc. (the ?Company?) in accordance with Section 16(a) of the Securities
Exchange Act of 1934 and any rule or regulation thereunder.

The authority of the Designees under this Statement shall continue until the
undersigned is no longer required to file Forms 3, 4, and 5 with
respect to the undersigned?s holdings of and/or transactions in securities of
the Company, unless earlier revoked by the undersigned in a signed writing
delivered to the Designees.  The undersigned acknowledges that the
Designees are not assuming, nor is the Company assuming, any of the
undersigned?s responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.  This Statement is not intended to be a power of
attorney as defined in the New York General Obligations Law, Article
5, Title 15, Section 5-1501, and in the event this Statement is determined to
be a power of attorney under such statute, this Statement shall not revoke
any power of attorney previously executed by the undersigned and shall not
be revoked by any subsequent power of attorney unless such subsequent
power of attorney expressly provides that it revokes this Statement by
referring to the date and subject hereof.


Date: May 21, 2018

    /s/   Joseph F. Serbun
Name:  Joseph F. Serbun




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