CVE-2026-28759

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

CVE-2026-28759

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

CVE-2026-28759

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

PT-2026-41640

Name of the Vulnerable Software and Affected Versions Mattermost versions 11.5.0 through 11.5.1 Mattermost versions 10.11.0 through 10.11.13 Mattermost versions 11.4.0 through 11.4.3 Description An issue exists during shared channel membership sync where the system fails to validate if a remote...

CVE-2026-41662 Admidio: Missing Minimum Administrator Check in Role Membership Removal

Admidio is an open-source user management solution. Prior to version 5.0.9, Role::stopMembership does not verify whether removing a user from the administrator role leaves zero administrators. The deprecated Membership::stopMembership contains this safety check, but the current code path bypasses...

CVE-2026-41662 Admidio: Missing Minimum Administrator Check in Role Membership Removal

Admidio is an open-source user management solution. Prior to version 5.0.9, Role::stopMembership does not verify whether removing a user from the administrator role leaves zero administrators. The deprecated Membership::stopMembership contains this safety check, but the current code path bypasses...

Admidio Missing Minimum Administrator Check in Role Membership Removal

Summary Role::stopMembership does not verify whether removing a user from the administrator role leaves zero administrators. The deprecated Membership::stopMembership contains this safety check, but the current code path bypasses it. Any administrator can remove the last remaining other...