CVE-2025-13821: Mattermost fails to sanitize sensitive data in WebSocket messages

February 16, 2026 (updated February 19, 2026)

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to sanitize sensitive data in WebSocket messages which allows authenticated users to exfiltrate password hashes and MFA secrets via profile nickname updates or email verification events. Mattermost Advisory ID: MMSA-2025-00560

References

github.com/advisories/GHSA-pp9j-pf5c-659x
github.com/mattermost/mattermost
github.com/mattermost/mattermost/commit/cd17b61de41bf0a49b524bb91ce0bbe859e5a100
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2025-13821

Code Behaviors & Features

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