CVE-2026-28735
MEDIUM
mattermost
mattermost_server
NVD
CVSS Score
5.4
Severity
MEDIUM
Published
May 22, 2026
Vendor
mattermost
Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628