CVE-2025-14573: Mattermost Auth Bypass Vulnerability

CVE-2025-14573 Overview

CVE-2025-14573 is an authorization bypass vulnerability affecting Mattermost Server versions 10.11.x through 10.11.9. The vulnerability stems from improper enforcement of invite permissions when updating team settings, allowing team administrators without appropriate permissions to bypass restrictions and add unauthorized users to their team via direct API requests.

Critical Impact

Team administrators can bypass invite permission restrictions and add users to teams without proper authorization, potentially compromising team privacy and access controls.

Affected Products

• Mattermost Server versions 10.11.x through 10.11.9

Discovery Timeline

• 2026-02-16 - CVE-2025-14573 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2025-14573

Vulnerability Analysis

This vulnerability is classified as CWE-862 (Missing Authorization), indicating that the Mattermost Server fails to properly verify authorization before allowing certain operations on team settings. The flaw exists in the team settings update functionality, where the API endpoint responsible for processing team membership changes does not adequately validate whether the requesting team administrator has been granted invite permissions.

When a team administrator attempts to modify team settings or add users through the API, the system should verify that the administrator possesses the specific invite permissions required for such actions. However, the affected versions fail to perform this authorization check, allowing administrators to directly invoke API calls that add users to their teams regardless of their actual permission level.

Root Cause

The root cause of this vulnerability is a missing authorization check in the team settings update API endpoint. The Mattermost Server does not properly enforce the invite permissions model when processing API requests that modify team membership. This oversight allows team administrators to bypass the configured permission restrictions by directly calling the underlying API endpoints rather than using the standard user interface, which may enforce these restrictions at a different layer.

Attack Vector

An attacker with team administrator privileges (but without invite permissions) can exploit this vulnerability by crafting direct API requests to the Mattermost Server. The attack requires network access to the Mattermost API and valid authentication credentials for a team administrator account.

The exploitation flow involves:

1. The attacker authenticates as a team administrator who lacks invite permissions
2. The attacker identifies the API endpoint used for updating team settings or adding team members
3. The attacker sends a crafted API request to add users to the team
4. The server processes the request without validating invite permissions
5. Unauthorized users are added to the team

This is a low-complexity attack that requires no user interaction, but does require high privileges (team administrator role) to execute.

Detection Methods for CVE-2025-14573

Indicators of Compromise

• Unexpected user additions to teams by administrators who should not have invite permissions
• API audit logs showing team membership changes from administrators without invite privileges
• Discrepancies between configured team invite permissions and actual user additions
• Unusual patterns of direct API calls to team settings endpoints bypassing the web interface

Detection Strategies

• Review Mattermost audit logs for team membership changes initiated by administrators lacking invite permissions
• Implement monitoring for API calls to team settings endpoints that result in user additions
• Compare team administrator permission configurations against actual team membership modification activities
• Set up alerts for bulk or unusual team membership changes via API endpoints

Monitoring Recommendations

• Enable comprehensive API logging on the Mattermost Server to capture all team settings modification requests
• Regularly audit team administrator permissions and compare against actual team membership changes
• Monitor for patterns of API-based team modifications that bypass normal UI workflows
• Implement periodic reviews of team membership to identify unauthorized additions

How to Mitigate CVE-2025-14573

Immediate Actions Required

• Upgrade Mattermost Server to a patched version beyond 10.11.9
• Review current team memberships to identify any unauthorized user additions
• Audit team administrator permissions and ensure invite permissions are properly configured
• Monitor API logs for any suspicious team settings modification activity

Patch Information

Mattermost has addressed this vulnerability in versions after 10.11.9. Administrators should consult the Mattermost Security Updates page for specific patch details and upgrade instructions. The advisory tracking this issue is MMSA-2025-00561.

Workarounds

• Restrict API access to trusted networks or implement additional API gateway controls
• Implement network-level monitoring to detect unusual API call patterns targeting team settings endpoints
• Temporarily revoke team administrator privileges from accounts that do not require them
• Consider implementing additional access controls or API rate limiting at the network layer

# Review team administrator permissions in Mattermost
# Check system config for team settings restrictions
mmctl config get TeamSettings.RestrictTeamInvite

# Audit team memberships for unauthorized additions
mmctl team list

# Review API audit logs for suspicious activity
grep "team" /opt/mattermost/logs/mattermost.log | grep "update"