CVE-2025-25279: Arbitrary File Access in Mattermost Server

The Arbitrary File Access vulnerability in Mattermost Server allows an attacker to read files that they should not have access to. This can occur during the board import process. An attacker could leverage this to read configuration files, source code, or other sensitive data stored on the server's file system. The potential impact includes data breaches, intellectual property theft, and potential escalation of privileges if sensitive credentials are exposed. The severity is critical due to the ease of exploitation and the potential for widespread data compromise, particularly in environments where sensitive information is stored on the Mattermost server.

1. Reserved2025-02-18
2. Published2025-03-03
3. Modified2026-02-04
4. EPSS updated2026-04-02

The primary mitigation for CVE-2025-25279 is to upgrade Mattermost Server to version 9.11.8+incompatible or later. Before upgrading, it is crucial to review Mattermost's upgrade documentation to ensure compatibility with your existing infrastructure and to avoid potential breaking changes. As a temporary workaround, restrict access to the board import functionality to trusted users only. Monitor Mattermost server logs for any unusual file access attempts. Consider implementing a Web Application Firewall (WAF) with rules to block suspicious file access requests related to board imports.