CVE-2026-2458

Mattermost versions 11.3.x = 11.3.0, 11.2.x = 11.2.2, 10.11.x = 10.11.10 fail to properly validate team membership when searching channels which allows a removed team member to enumerate all public channels within a private team via the channel search API endpoint.. Mattermost Advisory ID:...

CVE-2025-14350 Information disclosure via channel mentions in posts

Mattermost versions 11.1.x = 11.1.2, 10.11.x = 10.11.9, 11.2.x = 11.2.1 fail to properly validate team membership when processing channel mentions which allows authenticated users to determine the existence of teams and their URL names via posting channel shortlinks and observing the...

CVE-2025-14350

Mattermost versions 11.1.x = 11.1.2, 10.11.x = 10.11.9, 11.2.x = 11.2.1 fail to properly validate team membership when processing channel mentions which allows authenticated users to determine the existence of teams and their URL names via posting channel shortlinks and observing the...

PT-2026-8340

Name of the Vulnerable Software and Affected Versions Mattermost versions 10.11.x through 10.11.9 Mattermost versions 11.1.x through 11.1.2 Mattermost versions 11.2.x through 11.2.1 Description The software does not properly validate team membership when processing channel mentions. This allows...

CVE-2025-11777

Mattermost versions 10.11.x = 10.11.3, 10.5.x = 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint...

Incorrect Authorization

Overview Affected versions of this package are vulnerable to Incorrect Authorization due to properly validating team membership permissions in the Add Channel Member API. An attacker can obtain unauthorized access to user metadata and channel membership information from other teams by sending...

EUVD-2025-175343

Mattermost versions 10.11.x = 10.11.3, 10.5.x = 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint...

CVE-2025-11777 Cross-team channel membership access

Mattermost versions 10.11.x = 10.11.3, 10.5.x = 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint...

EUVD-2023-58777

Malicious code in bioql PyPI...

Code injection

Mattermost fails to validate team membership when a user attempts to access a playbook, allowing a user with permissions to a playbook but no permissions to the team the playbook is on to access and modify the playbook. This can happen if the user was once a member of the team, got permissions to...

CVE-2023-6547 Playbooks access/modification by removed team member

Mattermost fails to validate team membership when a user attempts to access a playbook, allowing a user with permissions to a playbook but no permissions to the team the playbook is on to access and modify the playbook. This can happen if the user was once a member of the team, got permissions to...