pallets/werkzeug · Security
Werkzeug safe_join() allows Windows special device names
- GHSA ID
- GHSA-g6x2-hccm-hh4m
- CVE ID
- CVE-2026-102598
- Severity
- medium
- Published
- Updated
- CVSS v4
- 6.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Description
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.
CWEs
- CWE-67 · Improper Handling of Windows Device Names
References
- 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/releases/tag/3.1.9 ↗
- https://github.com/advisories/GHSA-g6x2-hccm-hh4m ↗