CVE-2026-9859

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request...

CVE-2026-9859

Mattermost Boards plugin (versions ≤11.7.6, ≤10.11.21, ≤11.8.3) fails to enforce PermissionManageBoardRoles on the batch endpoint's channelId field, allowing authenticated board editors to relink boards to arbitrary channels via crafted PATCH requests. CVSS 3.1 scores 6.5 (MEDIUM) for network-bas...

PT-2026-76877

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request...