Disclosure summary
Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.
Source-reported weakness categories
CWE-67
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
GitHub Reviewed Security Advisories · GHSA-g6x2-hccm-hh4m
Open original source · Updated Oct 05, 2026
Werkzeug safe_join() allows Windows special device names
Source severity: MEDIUM / 6.3
| Ecosystem | Package | Affected range | First patched |
|---|---|---|---|
| pip | Werkzeug | < 3.1.9 | 3.1.9 |
NIST National Vulnerability Database · NVD-CVE-2026-102598
Open original source · Updated Sep 30, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
Original records & references
PUBLISHED 2026-09-29T12:17:06-04:00
MODIFIED 2026-09-30T15:38:27-04:00
INGESTED 2026-10-06T11:43:05-04:00