Description
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, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Mattermost Mattermost
Default version status: unaffected
11.7.0 to ≤ 11.7.6affected10.11.0 to ≤ 10.11.21affected11.8.0 to ≤ 11.8.3affected11.9.0unaffected11.7.7unaffected10.11.22unaffected11.8.4unaffected