Executive brief
Nextcloud is an open-source platform used by organizations for file sharing and collaboration. A security flaw in the file locking system allows logged-in users to lock or unlock files belonging to other people without permission. This could disrupt business operations by preventing legitimate users from editing their documents or by removing protections intended to prevent simultaneous file edits.
Technical details
An improper authentication vulnerability (CWE-287) exists in the Nextcloud 'files_lock' application due to insufficient ownership validation during WebDAV lock and unlock requests. By targeting absolute WebDAV paths, an authenticated attacker can manipulate file locks belonging to other users. Furthermore, the application leaks lock tokens in error responses, which allows unauthorized callers to bypass and remove token-based locks established by other client applications. The issue is resolved in Nextcloud Server versions 32.0.2 and 33.0.1, and Enterprise Server versions 31.0.14.4, 32.0.2, and 33.0.1.
Affected products
- Nextcloud Nextcloud Server 32.0.0 to < 32.0.2, 33.0.0 to < 33.0.1
- Nextcloud Nextcloud Enterprise Server 31.0.0 to < 31.0.14.4, 32.0.0 to < 32.0.2, 33.0.0 to < 33.0.1
Timeline
- 2026-02-24: patched: Fix merged in files_lock repository
- 2026-05-12: advisory: GitHub security advisory published
- 2026-06-01: disclosed: NVD publication date