CVE-2025-1792 is a security vulnerability identified in Mattermost, an open-source collaboration and messaging platform widely used for team communication. The vulnerability affects Mattermost versions 10.7.0, 10.5.0, and 9.11.0, specifically impacting the access control mechanisms for guest users. The flaw lies in the improper enforcement of authorization checks when guest users attempt to access channel member information via the channel members API endpoint. Due to this incorrect authorization (CWE-863), authenticated guest users can retrieve metadata about members of public channels, which they should not normally be permitted to view. This metadata exposure does not include sensitive personal data or credentials but may reveal user identifiers, roles, or other non-confidential information related to channel members. The vulnerability has a CVSS 3.1 base score of 3.1, indicating a low severity level. The vector details specify that the attack can be performed remotely over the network (AV:N), requires low privileges (PR:L), has high attack complexity (AC:H), does not require user interaction (UI:N), and impacts confidentiality only (C:L), without affecting integrity or availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The issue is primarily an information disclosure vulnerability due to insufficient access control validation for guest users in public channels, which could be leveraged to gather intelligence about team members or organizational structure.

For European organizations using affected versions of Mattermost, this vulnerability could lead to unintended exposure of user metadata within public channels to guest users. While the information disclosed is limited and does not include sensitive personal data or credentials, it could still aid an attacker in reconnaissance activities, such as mapping organizational structures, identifying active users, or profiling communication patterns. This could be a stepping stone for more targeted social engineering or phishing attacks. The impact is more pronounced in organizations with strict data privacy requirements under regulations like GDPR, where even limited unauthorized data exposure can have compliance implications. However, since the vulnerability does not affect data integrity or availability, the operational disruption risk is minimal. The low severity score reflects the limited scope and complexity of exploitation, but organizations should still consider the risk in environments where guest access is enabled and public channels contain sensitive operational information.

European organizations should promptly assess their Mattermost deployments to identify if they are running affected versions (10.7.0, 10.5.0, 9.11.0). Until official patches are released, organizations can mitigate risk by restricting guest user access to public channels or disabling guest accounts where feasible. Implementing network-level controls to limit guest user API access can also reduce exposure. Administrators should review channel membership and metadata visibility settings to ensure minimal information is exposed to guest users. Monitoring API access logs for unusual guest user activity targeting channel member endpoints can help detect exploitation attempts. Additionally, organizations should plan to upgrade Mattermost to the latest secure versions once patches become available. Incorporating strict role-based access controls and periodic audits of user permissions will further reduce the risk of similar authorization flaws.