CVE-2026-9162: Mattermost doesn't invalidate cached authentication state for active WebSocket connections during global session revocation

June 22, 2026 (updated September 15, 2026)

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to invalidate cached authentication state for active WebSocket connections during global session revocation, which allows a user with an existing WebSocket connection to remain authenticated and continue receiving real-time events until the cached session expires or the client reconnects.. Mattermost Advisory ID: MMSA-2026-00664

References

github.com/advisories/GHSA-h998-hxxj-8q83
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-9162

Code Behaviors & Features

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