GHSA-g6x2-hccm-hh4m
Werkzeug safe_join() allows Windows special device names
At a glance
- Published
- Updated
- CVE
- CVE-2026-102598
- Aliases
- PYSEC-2026-4312
- CVSS_V4
- 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.
Affected packages
| Package | Versions |
|---|---|
| PyPI · werkzeug | introduced 0, fixed 3.1.9 |
References
- https://github.com/pallets/werkzeug/security/advisories/GHSA-g6x2-hccm-hh4m WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-102598 ADVISORY
- https://github.com/pallets/werkzeug/pull/3309 WEB
- https://github.com/pallets/werkzeug/commit/8d77320bcdf3a34941ec06dcf16b03c065cd21b6 WEB
- https://github.com/pallets/werkzeug PACKAGE
- https://github.com/pallets/werkzeug/releases/tag/3.1.9 WEB
Sources
| Source | Licence |
|---|---|
| OSV.dev | CC-BY 4.0 — GitHub Advisory Database |