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medium advisory

Mattermost Server: Multiple security vulnerabilities

Multiple unspecified vulnerabilities have been identified in Mattermost Server, requiring immediate review of vendor security bulletins and application of necessary patches.

Triage facts

Revision 1
Applicability
Mattermost Server (11.10.x < 11.10.3), Mattermost Server (11.11.x < 11.11.2) +1
Evidence
Unknown
Severity
Medium
Action
Elevated
Sources
2 public sources
Freshness
Revision 1Oct 21, 16:07 UTC
Source quality
A1Likely

The French National Cybersecurity Agency (ANSSI) has published an advisory regarding multiple unspecified vulnerabilities in Mattermost Server. These vulnerabilities, identified in Mattermost security bulletins MMSA-2026-00772 and MMSA-2026-00783, could allow an attacker to trigger unspecified security issues. Details regarding specific vulnerability types or exploitation vectors remain undisclosed by the vendor.

Recommendation

  • Inventory all internal Mattermost Server instances to identify versions 11.10.x, 11.11.x, and 11.7.x.
  • Upgrade Mattermost Server instances to the following patched versions immediately:
  • Upgrade version 11.10.x to 11.10.3 or later.
  • Upgrade version 11.11.x to 11.11.2 or later.
  • Upgrade version 11.7.x to 11.7.13 or later.
  • Monitor the official Mattermost Security Updates portal for further technical disclosures.

Immediate actions

Patch Mattermost Server to the versions specified in the bulletin

IT Operations 48h

Mitigations

Upgrade Mattermost Server to 11.10.3, 11.11.2, or 11.7.13 depending on the branch

immediate IT Operations

Mattermost Server versions 11.10.x, 11.11.x, and 11.7.x