CVE-2025-66221
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 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. This issue has been patched in version 3.1.4.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 6.3
- CVSS vector
- 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
- EPSS probability
- 0.51%
- CWE
- CWE-67
- Published
- 2025-11-29
- Last modified
- 2026-03-13
Affected products
- pallets werkzeug
Weakness type
Related vulnerabilities
- CVE-2026-27199 — Werkzeug safe_join() allows Windows special device names
- CVE-2026-21860 — Werkzeug safe_join() allows Windows special device names with compound extensions
- CVE-2024-51745 — Wasmtime doesn't fully sandbox all the Windows device filenames
- CVE-2024-35197 — gix refs and paths with reserved Windows device names access the devices