CVE-2026-9693
LowCVSS 3.5Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
Mattermost versions 10.11.x <= 10.11.20 and 11.7.x <= 11.7.5 fail to remove thread membership records when a user is removed from or leaves a team, allowing a previously removed user who is later re-invited to view private channel thread root post content and metadata via the team threads API.
Risk Assessment
The risk is unauthorized access to private channel content after re-invitation, potentially compromising confidentiality of conversations.
Recommendation
Update Mattermost to a patched version and review user permissions after re-adding to a team.
Original NVD description (English source)
Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682