Mattermost 11.0.4/10.12.2/10.11.6 DoS via WS UTF8 Check Failure
CVE-2025-12689 Published on December 17, 2025
DoS in Calls plugin via malformed UTF-8 in WebSocket request
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.
Vulnerability Analysis
CVE-2025-12689 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
Improper Validation of Specified Type of Input
The product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type.
Products Associated with CVE-2025-12689
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Affected Versions
Mattermost:- Version 11.0.0, <= 11.0.4 is affected.
- Version 10.12.0, <= 10.12.2 is affected.
- Version 10.11.0, <= 10.11.6 is affected.
- Version 11.1.0 is unaffected.
- Version 11.0.5 is unaffected.
- Version 10.12.3 is unaffected.
- Version 10.11.7 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.