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

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-2026-16047 Board channel linking without read channel permission validation

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing...

EUVD-2026-60208

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing...

CVE-2026-16047

Mattermost versions 11.7.x ≤ 11.7.6, 10.11.x ≤ 10.11.21, and 11.8.x ≤ 11.8.3 contain an authorization flaw in the board-to-channel linking functionality. The server fails to verify that the requesting user has read access to a target channel before associating a board with it. An authenticated us...

CVE-2026-16046 Missing run-state validation on finished playbook runs

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to enforce run-state validation on write operations for finished playbook runs which allows a run participant to modify status, checklists, retrospective content, ownership, and participants on completed runs via REST and GraphQL API...

CVE-2026-16046

Mattermost versions 11.7.x ≤ 11.7.6 and 10.11.x ≤ 10.11.21 lack run-state validation on write operations for completed playbook runs, enabling authenticated participants to alter status, checklists, retrospective content, ownership, and participants via REST and GraphQL APIs. No patch version or ...

EUVD-2026-60207

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to enforce run-state validation on write operations for finished playbook runs which allows a run participant to modify status, checklists, retrospective content, ownership, and participants on completed runs via REST and GraphQL API...

CVE-2026-16048

Mattermost versions 11.8.x through 11.8.2, 11.7.x through 11.7.6, and 10.11.x through 10.11.21 fail to restrict the channel member roles API to channel-scoped roles, allowing a channel administrator to assign out-of-scope roles and gain additional permissions. Advisory MMSA-2026-00697 tracks the ...

CVE-2026-16048 Channel member roles accept out-of-scope roles

Mattermost versions 11.8.x = 11.8.2, 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to restrict channel member role assignment to channel-scoped roles which allows a channel administrator to gain additional channel permissions via the channel member roles API.. Mattermost Advisory ID: MMSA-2026-00697...

EUVD-2026-60206

Mattermost versions 11.8.x = 11.8.2, 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to restrict channel member role assignment to channel-scoped roles which allows a channel administrator to gain additional channel permissions via the channel member roles API.. Mattermost Advisory ID: MMSA-2026-00697...

CVE-2026-16048

Mattermost versions 11.8.x = 11.8.2, 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to restrict channel member role assignment to channel-scoped roles which allows a channel administrator to gain additional channel permissions via the channel member roles API.. Mattermost Advisory ID: MMSA-2026-00697...

PT-2026-76876

Name of the Vulnerable Software and Affected Versions Mattermost versions 11.7.0 through 11.7.6 Mattermost versions 10.11.0 through 10.11.21 Mattermost versions 11.8.0 through 11.8.3 Description Insufficient server-side validation of BoardMember.Scheme fields during insert and archive-import...

PT-2026-76669

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:...

PT-2026-76667

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fails to reconcile SchemeAdmin flags with a user's current role which allows a user demoted to System Guest to retain Board Admin privileges and perform admin-only operations via the Boards REST API or UI.. Mattermost Adviso...

PT-2026-76668

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...

PT-2026-76671

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 post id , and fails to validate the web url parameter against the configured GitLab instance, which allows an authenticated...

PT-2026-76875

Name of the Vulnerable Software and Affected Versions Mattermost versions 10.11.0 through 10.11.20 Mattermost versions 11.7.0 through 11.7.5 Description The software fails to remove thread membership records when a user leaves or is removed from a team. This allows a user who is subsequently...

PT-2026-76867

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fails to validate WebSocket command field types which allows an authenticated user to crash the plugin process and deny service to all Boards users via a custom focalboard SUBSCRIBE TEAM message with a non-string teamId...