CVE-2026-39942

Summary

A broken access control vulnerability was identified in the Directus file management API that allows authenticated users to overwrite files belonging to other users by manipulating the filename_disk parameter.

Details

The PATCH /files/{id} endpoint accepts a user-controlled filename_disk parameter. By setting this value to match the storage path of another user's file, an attacker can overwrite that file's content while manipulating metadata fields such as uploaded_by to obscure the tampering.

Impact

• Unauthorized File Overwrite: Attackers can replace legitimate files with malicious content, creating significant risk of malware propagation and data corruption.
• Remote Code Execution: If the storage backend is shared with the extensions location, attackers can deploy malicious extensions that execute arbitrary code when loaded.
• Data Integrity Compromise: Files can be tampered with or replaced without visible indication in the application interface.

Mitigation

The filename_disk parameter should be treated as a server-controlled value. Uniqueness of storage paths must be enforced server-side, and filename_disk should be excluded from the fields users are permitted to update directly.