EUVD-2026-16162
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Lifecycle Timeline
4Description
Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574
Analysis
Mattermost versions 11.2.x through 11.2.2, 10.11.x through 10.11.10, 11.4.0, and 11.3.x through 11.3.1 fail to properly restrict team-level access during remote cluster membership synchronization, allowing a malicious remote cluster to grant users access to entire private teams rather than limiting access to only shared channels. An authenticated attacker controlling a federated remote cluster can send crafted membership sync messages to trigger unintended team membership assignment, resulting in unauthorized access to private team resources. …
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Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.
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Priority Score
Vendor Status
Debian
Bug #823556| Release | Status | Fixed Version | Urgency |
|---|---|---|---|
| open | - | - |
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External POC / Exploit Code
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