CVE-2025-9076

Mattermost Server exposes sensitive user credentials during shared channel membership synchronization

Published Sep 15, 2025 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Description
Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization, which allows malicious or compromised remote clusters to access sensitive user information via unsanitized user objects. This vulnerability affects Mattermost Server instances with shared channels enabled.

Remediation

Vendor Solution

Update Mattermost to versions 10.11.0, 10.10.2 or higher.

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2025-29165 Mattermost Missing Authorization vulnerability
Github GHSA Github GHSA GHSA-3vcm-c42p-3hhf Mattermost Missing Authorization vulnerability
References
History
Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server
Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization, which allows malicious or compromised remote clusters to access sensitive user information via unsanitized user objects. This vulnerability affects Mattermost Server instances with shared channels enabled.
Title Mattermost Server exposes sensitive user credentials during shared channel membership synchronization
Weaknesses CWE-862
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
Sep 15, 2025, 2:05 PM
Reserved
Aug 15, 2025, 3:26 PM
Status
Analyzed
Published
Sep 15, 2025, 10:15 AM
Modified
Oct 19, 2026, 5:10 PM