Mattermost Server: Multiple Security Vulnerabilities
Mattermost has released security updates addressing multiple unspecified vulnerabilities across several server versions, requiring immediate patching.
Triage facts
Revision 1- Applicability
- Mattermost Server (11.10.x < 11.10.5), Mattermost Server (11.11.x < 11.11.4) +2
- Evidence
- Unknown
- Severity
- High
- Action
- Elevated
- Sources
- 2 public sources
- Freshness
- Revision 1Nov 9, 16:12 UTC
- Source quality
- A1Roughly even chance
The French National Cybersecurity Agency (ANSSI) has issued an advisory regarding multiple vulnerabilities in Mattermost Server. These issues were disclosed in Mattermost security bulletins MMSA-2026-00592, MMSA-2026-00781, and MMSA-2026-00786. The vendor has not provided specific details regarding the nature of the vulnerabilities or their potential impact.
Recommendation
- Inventory all deployed Mattermost Server instances to identify affected versions.
- Upgrade Mattermost Server instances to the latest secure versions as defined by the vendor security bulletins.
- Monitor the official Mattermost security updates page for additional technical details as they become available.
Immediate actions
Patch affected Mattermost Server instances to the version ranges specified in MMSA-2026-00592, MMSA-2026-00781, and MMSA-2026-00786
Mitigations
Upgrade Mattermost Server to the latest release as specified by the vendor
Multiple unspecified vulnerabilities