Werkzeug safe_join() allows Windows special device names
Werkzeug's `safe_join` function allows path segments with Windows device names. On Windows, there are special device names such as `CON`, `AUX`, etc that are implicitly present and readable in every directory. `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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2025-66221US | medium5.3 | — | ||
Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.4, Werkzeug's safe_join function allows path segments with Windows device names. On Windows, there ar… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/advisories/GHSA-hgf8-39gv-g3f2ADVISORY
- https://github.com/pallets/werkzeugPACKAGE
- https://github.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0c13WEB
- https://github.com/pallets/werkzeug/releases/tag/3.1.4WEB
- https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2WEB
- https://nvd.nist.gov/vuln/detail/CVE-2025-66221ADVISORY
- https://pypi.org/project/werkzeugPACKAGE
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