Mattermost security advisory (AV26-828)
Brief
Serial Number: AV26-828
Date: August 18, 2026
As of August 17, 2026, Mattermost is affected by vulnerabilities in the following product:
- Mattermost
- Prior to or equal to 10.11.21
- Prior to or equal to 11.7.6
- Prior to or equal to 11.8.3
The Cyber Centre encourages users and administrators to review the provided web links and apply any necessary updates as they become available.
- CVE-2026-9816 Detail
- Mattermost Security Updates
Mattermost security advisory (AV26-828) - Canadian Centre for Cyber Security