CVE-2026-9162
Received Received - Intake
Authentication Bypass in Mattermost via Cached WebSocket Sessions

Publication date: 2026-06-22

Last updated on: 2026-06-22

Assigner: Mattermost, Inc.

Description
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
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Meta Information
Published
2026-06-22
Last Modified
2026-06-22
Generated
2026-06-22
AI Q&A
2026-06-22
EPSS Evaluated
N/A
NVD
CVE-2026-9162
EUVD
EUVD-2026-38247
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
mattermost 11.7 to 11.7.0 (inc)
mattermost 11.6 to 11.6.2 (inc)
mattermost 11.5 to 11.5.5 (inc)
mattermost 10.11 to 10.11.17 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-613 According to WASC, "Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization."
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Executive Summary

This vulnerability affects certain versions of Mattermost where the system fails to invalidate cached authentication states for active WebSocket connections during a global session revocation.

As a result, a user who already has an active WebSocket connection can remain authenticated and continue to receive real-time events even after their session has been revoked, until the cached session expires or the client reconnects.

Impact Analysis

The impact of this vulnerability is that a user with an active WebSocket connection may continue to have access to real-time data and events despite their session being globally revoked.

This could lead to unauthorized access to information or continued interaction with the system beyond the intended session lifetime.

According to the CVSS score, the impact on confidentiality is low, with no impact on integrity or availability.

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