CVE-2025-14573: 
vulnerability analysis and mitigation

CVE-2025-14573 is a missing authorization vulnerability in Mattermost Server that allows team administrators without proper invite permissions to bypass restrictions and add users to their team via API requests. It affects Mattermost Server versions 10.11.0 through 10.11.9 (inclusive), and is tracked under Mattermost Advisory ID MMSA-2025-00561. The vulnerability was published on February 16, 2026, with a patch released in version 10.11.10. It carries a CVSS v3.1 base score of 2.7 (Low) (Red Hat CVE, Mattermost Security).

The root cause is classified as CWE-862 (Missing Authorization): Mattermost Server fails to enforce invite permission checks when processing API requests that update team settings, specifically the allowOpenInvite field. A team administrator — who would otherwise lack the privilege to invite users — can craft API requests to modify team settings and add users, bypassing the intended permission model. No authentication bypass is required; the attacker must already hold a team administrator role, making this an authorization enforcement gap rather than an authentication flaw (Red Hat CVE, Infinitsec).

Exploitation allows a team administrator without proper invite permissions to add unauthorized users to a Mattermost team, resulting in unauthorized access to team channels, messages, files, and other shared resources. The integrity impact is limited to team membership modification, with no direct confidentiality or availability impact assessed. While lateral movement potential is low, unauthorized team membership could expose sensitive organizational communications to unintended parties (Red Hat CVE).

1. Obtain team administrator access: The attacker must already hold a team administrator role within the target Mattermost instance (legitimate or compromised credentials).
2. Identify the target team: Determine the team ID for the team the attacker administers, using the Mattermost API or UI.
3. Craft a malicious API request: Send an authenticated API request to the team settings update endpoint (e.g., PUT /api/v4/teams/{team_id}) with the allow_open_invite or related invite permission field set to enable open invitations, bypassing server-side permission enforcement.
4. Add unauthorized users: With invite restrictions bypassed, use the team invite API to add users who would otherwise be restricted from joining the team.
5. Access team resources: The newly added users can now access team channels, messages, and files (Infinitsec, Red Hat CVE).

• Logs: Mattermost audit logs showing PUT /api/v4/teams/{team_id} requests from team administrator accounts that modify invite-related settings (allow_open_invite) without corresponding system administrator authorization.
• Logs: Unexpected team membership additions logged in Mattermost audit trails, particularly for users who were previously restricted from joining.
• Network: API calls to team settings update endpoints originating from team administrator accounts at unusual times or frequencies.
• Application: Sudden increase in team membership for teams with restricted invite policies, especially if new members were not added through normal administrative workflows (Red Hat CVE, Mattermost Security).

Mattermost has released a patch in version 10.11.10, which enforces proper invite permission checks during team settings updates. Organizations should upgrade Mattermost Server to version 10.11.10 or later immediately. As interim measures, administrators should review team administrator permissions, audit recent team membership changes for unauthorized additions, and monitor API requests related to team settings updates for suspicious activity (Mattermost Security, Red Hat CVE).