Remote Image Processing Flaw in Mattermost Server Versions
CVE-2026-16251

6.5MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 October 2026

What is CVE-2026-16251?

Certain versions of Mattermost Server are vulnerable due to inadequate limitations on the size of remote image responses during local image proxy fetches. This shortcoming allows an attacker to exploit the system by sending a malicious oversized image, leading to memory exhaustion on the server and potentially causing service interruptions. It is crucial for users to review their versions and implement the necessary updates to mitigate this risk.

Affected Version(s)

Mattermost 11.10.0

Mattermost 11.7.0 <= 11.7.9

Mattermost 11.9.0 <= 11.9.1

References

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

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

alimursaliyev
.