Mattermost Server Vulnerability Leading to OOM Errors
CVE-2026-2454

5.8MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 March 2026

What is CVE-2026-2454?

Certain versions of Mattermost Server are susceptible to a vulnerability that arises from improper handling of incorrectly reported array lengths. An attacker could exploit this flaw by sending malformed msgpack frames through websocket connections, leading to out-of-memory (OOM) errors. This condition can effectively crash the server, thereby disrupting services for legitimate users. For more details, refer to the Mattermost Advisory ID: MMSA-2025-00537.

Affected Version(s)

Mattermost 11.3.0

Mattermost 11.2.0 <= 11.2.2

Mattermost 10.11.0 <= 10.11.10

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
5.8
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

National Security Agency
.