CVE-2026-15754 Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal

Mattermost versions 11.7.x = 11.7.6, 11.8.x = 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC attribute-based access control policy...

CVE-2026-15754

Mattermost 11.7.x (≤11.7.6) and 11.8.x (≤11.8.3) have a missing per-channel team-scope check in the ABAC policy unassign endpoint, allowing an authenticated team administrator to remove ABAC policy assignments from channels that have been moved to another team. Impact is integrity-focused (CVSS 4...

CVE-2026-15754 Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal

Mattermost versions 11.7.x = 11.7.6, 11.8.x = 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC attribute-based access control policy...

CVE-2026-15754

Mattermost versions 11.7.x = 11.7.6, 11.8.x = 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC attribute-based access control policy...

EUVD-2026-60212

Mattermost versions 11.7.x = 11.7.6, 11.8.x = 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC attribute-based access control policy...

CVE-2026-16044 Insufficient validation of guest board admin privileges on archive import

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID:...

CVE-2026-16044

Mattermost versions 11.7.6 and 10.11.21 fail to validate guest user privileges during board archive import, allowing a board member to escalate a guest user to Board Admin via a crafted .boardarchive file. CVSS 5.4 (MEDIUM). No exploitation details or patch version are provided. Upgrade to a fixe...

CVE-2026-16044 Insufficient validation of guest board admin privileges on archive import

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID:...

EUVD-2026-60211

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID:...

CVE-2026-16044

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID:...

EUVD-2026-60210

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 Mattermost failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions, which allowed an OAuth app with a delegated user token to revoke the user's authorizations or tokens for other...

CVE-2026-16045 Delegated OAuth tokens could revoke unrelated OAuth application authorizations

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 Mattermost failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions, which allowed an OAuth app with a delegated user token to revoke the user's authorizations or tokens for other...

CVE-2026-16045

Mattermost 11.7.x (≤11.7.6) and 10.11.x (≤10.11.21) failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions. A malicious OAuth app holding a delegated user token could revoke the user's authorizations or tokens for unrelated integrations via...

CVE-2026-16045

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 Mattermost failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions, which allowed an OAuth app with a delegated user token to revoke the user's authorizations or tokens for other...

CVE-2026-16045 Delegated OAuth tokens could revoke unrelated OAuth application authorizations

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 Mattermost failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions, which allowed an OAuth app with a delegated user token to revoke the user's authorizations or tokens for other...

EUVD-2026-60209

Mattermost Plugins versions =11.8 10.20.11 11.5.7.0 The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied postid, and fails to validate the weburl parameter against the configured GitLab instance, which allows an authenticated attacke...

CVE-2026-16049 _GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_

Mattermost Plugins versions =11.8 10.20.11 11.5.7.0 The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied postid, and fails to validate the weburl parameter against the configured GitLab instance, which allows an authenticated attacke...

CVE-2026-16049

The Mattermost GitLab plugin (versions ≤11.8, 10.20.11, 11.5.7.0) fails to verify channel permissions for caller-supplied post_id and does not validate the web_url parameter against the configured GitLab instance. Through the createIssue and attachCommentToIssue API endpoints, an authenticated at...

CVE-2026-16049

Mattermost Plugins versions =11.8 10.20.11 11.5.7.0 The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied postid, and fails to validate the weburl parameter against the configured GitLab instance, which allows an authenticated attacke...

CVE-2026-16049 _GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_

Mattermost Plugins versions =11.8 10.20.11 11.5.7.0 The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied postid, and fails to validate the weburl parameter against the configured GitLab instance, which allows an authenticated attacke...