WebSocket Command Validation Flaw in Mattermost by Mattermost
CVE-2026-10080

6.5MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
17 August 2026

What is CVE-2026-10080?

A vulnerability exists in Mattermost that fails to properly validate the types of command fields in WebSocket messages. This issue allows authenticated users to initiate a denial of service attack by sending a custom_focalboard_SUBSCRIBE_TEAM message containing a non-string teamId. As a result, this can crash the plugin process, denying service to all users accessing Boards. This affects specific versions of Mattermost, making it crucial for administrators to update their systems to mitigate potential disruptions.

Affected Version(s)

Mattermost 11.7.0 <= 11.7.6

Mattermost 10.11.0 <= 10.11.21

Mattermost 11.8.0 <= 11.8.3

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
.