GHSA-g6x2-hccm-hh4m
Werkzeug safe_join() allows Windows special device names
Packages
Details
As written in the advisory (Markdown source, shown as plain text).
Werkzeug's `safe_join` function allows Windows device names as filenames when they have an empty ADS marker on NTFS.
This was previously reported as https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact Windows allows special device names with an empty ADS marker, such as `NUL:`.
`send_from_directory` uses `safe_join` to safely serve files at user-specified paths under a directory. If the application is running on Windows and NTFS, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.
References
External links from the advisory. They lead to third-party sites.
- https://github.com/pallets/werkzeug/security/advisories/GHSA-g6x2-hccm-hh4m
- https://nvd.nist.gov/vuln/detail/CVE-2026-102598
- https://github.com/pallets/werkzeug/pull/3309
- https://github.com/pallets/werkzeug/commit/8d77320bcdf3a34941ec06dcf16b03c065cd21b6
- https://github.com/pallets/werkzeug
- https://github.com/pallets/werkzeug/releases/tag/3.1.9