CVE-2025-12689

DoS in Calls plugin via malformed UTF-8 in WebSocket request

CVSS 6.5 MEDIUMEPSS 0.2%CWE-1287

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 6.5EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

17 Dec 2025Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

Mattermost versions 11.0.x <= 11.0.4, 10.12.x <= 10.12.2, 10.11.x <= 10.11.6 fail to check WebSocket request field for proper UTF-8 format, which allows attacker to crash Calls plug-in via sending malformed request.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Mattermost · Mattermost

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References

https://mattermost.com/security-updates