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Mattermost CVE-2026-20796

LOW
Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367)
2026-02-13 responsibledisclosure@mattermost.com GHSA-2xf7-hmf6-p64j
3.1
CVSS 3.1

CVSS VectorNVD

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Lifecycle Timeline

3
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
Analysis Generated
Mar 12, 2026 - 22:02 vuln.today
CVE Published
Feb 13, 2026 - 11:16 nvd
LOW 3.1

DescriptionNVD

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

AnalysisAI

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549 [CVSS 3.1 LOW]

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RemediationAI

During next maintenance window: Apply vendor patches when convenient. Monitor vendor channels for updates.

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CVE-2026-20796 vulnerability details – vuln.today

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