CVE-2026-27199
Werkzeug safe_join() allows Windows special device names
- State
- Published
- Severity
- 6.3 Medium
- Published
- Feb 21, 2026
- Updated
- Feb 24, 2026
- Reserved
- Feb 18, 2026
Description
Werkzeug is a comprehensive WSGI web application library. Versions 3.1.5 and below, the safe_join function allows Windows device names as filenames if preceded by other path segments. This was previously reported as GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that safe_join accepts paths with multiple segments, such as example/NUL. The function 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 the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely. This issue has been fixed in version 3.1.6.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.3 Medium | 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 | GitHub_M |
Weaknesses
- CWE-67 Improper Handling of Windows Device Names
Affected Products
| Product | Versions |
|---|---|
werkzeugpallets |
|
References
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