Mattermost permite a leitura de arquivos arbitrários em github.com/mattermost/mattermost-server

The impact of this vulnerability is significant. An attacker who successfully exploits CVE-2025-20051 can read any file accessible by the Mattermost Server process. This includes configuration files, database backups, source code, and potentially even user data. The ability to read sensitive configuration files could reveal credentials or internal system details, facilitating further attacks. Exposure of database backups could lead to complete data compromise. The blast radius extends to any data stored or processed by the Mattermost Server instance.

Organizations using Mattermost Server for internal communication are at risk, particularly those with sensitive data stored or processed within the platform. Environments with lax file system permissions or those running older, unpatched versions of Mattermost Server are especially vulnerable. Shared hosting environments where Mattermost Server instances share the same file system as other applications also face increased risk.

• linux / server: Monitor Mattermost Server logs (typically /var/log/mattermost/mattermost.log) for unusual file access patterns or errors related to file reading. Use lsof to identify processes accessing files within the Mattermost data directory.

lsof /path/to/mattermost/data

• go: Examine Mattermost Server's source code for instances of file reading functions that lack proper validation. Look for patterns where user-supplied input is directly used in file paths. • generic web: Attempt to access arbitrary files using crafted URLs. For example, try accessing /file.txt or /../../../../etc/passwd to test for file access vulnerabilities. • windows / supply-chain: If Mattermost Server is deployed on Windows, monitor PowerShell execution logs for suspicious commands related to file access within the Mattermost data directory. Use Windows Defender to scan for malicious files associated with the vulnerability.

1. 2025-03-03Disclosure

   disclosure

1. Reservado2025-02-18
2. Publicada2025-03-03
3. Modificada2026-02-04
4. EPSS atualizado2026-04-02

The primary mitigation for CVE-2025-20051 is to upgrade to Mattermost Server version 9.11.8+incompatible or later. If immediate upgrading is not possible, consider implementing temporary workarounds such as restricting file system access for the Mattermost Server process. Review and harden file permissions to limit the potential impact of a successful exploit. Monitor Mattermost Server logs for any unusual file access attempts. After upgrade, confirm the vulnerability is resolved by attempting to access a restricted file and verifying that access is denied.