Executive brief
Filestash is a file management system accessible via web interface. An attacker can take over the administrative console of a freshly deployed Filestash instance before setup is completed by sending a crafted request to modify the admin password. This grants complete control over file storage, sharing permissions, and configuration settings.
Technical details
The vulnerability is an improper access control issue (CWE-284) in the AdminOnly middleware of Filestash. The middleware only enforces admin authentication checks when auth.admin is non-empty; during initial setup, this field is unset, allowing unauthenticated access to /admin/api/config. An attacker can issue GET /admin/api/config to retrieve the current configuration, modify the auth.admin password hash field with a bcrypt hash of their chosen password, and POST the modified JSON to persist the change. No authentication, user interaction, or elevated privileges are required; the only precondition is network reachability to the uninitialized instance. Successful exploitation results in complete administrative takeover of the application, including access to global configuration, storage definitions, secrets, and sharing behavior. As of the advisory publication, no patched version is available.
Affected products
- Mickael Kerjean Filestash <= 0.2.2-0.20260827111952-cbcd1e96ebc7
Timeline
- 2026-06-15: disclosed: Advisory published to GitHub
- 2026-08-27: advisory: GitHub reviewed and updated advisory