CVE-2025-10545 - CVE House
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Status published Low CVE-2025-10545

Guest user can add unauthorized team users to private channels

Vulnerability Description

Mattermost versions 10.5.x <= 10.5.10, 10.11.x <= 10.11.2 fail to properly validate guest user permissions when adding channel members which allows guest users to add any team members to their private channels via the `/api/v4/channels/{channel_id}/members` endpoint

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

  • lordwillmore

References

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Affected Vendor

Affected Software

Mattermost
Vulnerable Versions:
10.5.0, 10.11.0, 10.12.0, 10.5.11, 10.11.3

Timeline

Official Publish: October 16th, 2025
Last Modified: October 16th, 2025
Added to House: July 22nd, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

Weaknesses (CWE)

CWE-863

MITRE ATT&CK TTPs

T1190 Exploit Public-Facing Application
Initial Access
T1078 Valid Accounts
Persistence
T1548 Abuse Elevation Control Mechanism
Privilege Escalation
T1021 Remote Services
Lateral Movement
T1098 Account Manipulation
Defense Evasion