CVE-2026-9162: Global session revocation does not invalidate active WebSocket connections
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
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.8.0 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.7.1 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.6.3 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.5.6 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 10.11.18 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Patch MMSA-2026-00664
Event History
Frequently Asked Questions
What is the severity of CVE-2026-9162?
The severity of CVE-2026-9162 is classified as medium with a score of 4.3.
What does CVE-2026-9162 affect?
CVE-2026-9162 affects Mattermost versions 11.7.x up to 11.7.0, 11.6.x up to 11.6.2, 11.5.x up to 11.5.5, and 10.11.x up to 10.11.17.
How do I fix CVE-2026-9162?
To fix CVE-2026-9162, upgrade Mattermost to a version that is not affected, ensuring you are using a version higher than 11.7.0, 11.6.2, 11.5.5, or 10.11.17.
What is the main issue with CVE-2026-9162?
The main issue with CVE-2026-9162 is that it fails to invalidate cached authentication state for active WebSocket connections during global session revocation.
What could be the impact of CVE-2026-9162?
The impact of CVE-2026-9162 allows a user with an existing WebSocket connection to remain authenticated and potentially perform actions they should no longer have access to.