EUVD-2026-38276

Mattermost versions 11.7.x = 11.7.0, 10.11.x = 10.11.17 fail to validate bot targets when demoting users to guests which allows a lower-privileged administrator to degrade arbitrary bot accounts via the standard demote-user API.. Mattermost Advisory ID: MMSA-2026-00669...

EUVD-2026-12518

Mattermost versions 10.11.x = 10.11.10 fail to properly validate permission requirements in the team member roles API endpoint which allows team administrators to demote members to guest role. Mattermost Advisory ID: MMSA-2025-00531...

CVE-2025-53971 Channel and Team Membership APIs inadvertently allow loss of Member privileges.

Mattermost versions 10.5.x = 10.5.8, 9.11.x = 9.11.17 fail to properly validate authorization for team scheme role modifications which allows Team Admins to demote Team Members to Guests via the PUT /api/v4/teams/team-id/members/user-id/schemeRoles API endpoint...