CVE-2026-27199
Werkzeug safe_join() allows Windows special device names
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.
| CWE | CWE-67 |
| Vendor | pallets |
| Product | werkzeug |
| Published | Feb 21, 2026 |
| Last Updated | Feb 24, 2026 |
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