CVE-2026-16047

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 An authenticated attacker can discover the membership of private channels within the same team. This occurs because the system fails to validate if a user has read access to a channel before linking a board to it. The issue can be exploited by creating, patching, importing, or bulk-creating boards using an arbitrary channelId.

Recommendations Update Mattermost versions 11.7.0 through 11.7.6 to a version newer than 11.7.6. Update Mattermost versions 10.11.0 through 10.11.21 to a version newer than 10.11.21. Update Mattermost versions 11.8.0 through 11.8.3 to a version newer than 11.8.3.