CVE-2025-66221

29.11.2025, 03:16

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.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	NIST	5.3 MEDIUM	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub_M	CNA	---				---
CISA-ADP	ADP	---				---

Base Score

CVSS 3.x

EPSS Score

Percentile: 6%

Vendor	Product	Version
palletsprojects	werkzeug	𝑥 < 3.1.4

𝑥

= Vulnerable software versions

Debian Releases

Debian Product

Codename

python-werkzeug

bullseye	1.0.1+dfsg1-2+deb11u1 fixed
bullseye (security)	1.0.1+dfsg1-2+deb11u2 fixed
bookworm	2.2.2-3+deb12u1 fixed
trixie	3.1.3-2 fixed
forky	3.1.4-1 fixed
sid	3.1.5-1 fixed

Ubuntu Releases

Ubuntu Product

Codename

python-werkzeug

questing	not-affected
plucky	not-affected
noble	not-affected
jammy	not-affected
focal	not-affected
bionic	not-affected
xenial	not-affected

Common Weakness Enumeration

CWE-67 - Improper Handling of Windows Device Names
The software constructs pathnames from user input, but it does not handle or incorrectly handles a pathname containing a Windows device name such as AUX or CON. This typically leads to denial of service or an information exposure when the application attempts to process the pathname as a regular file.

References

https://github.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0c13

https://github.com/pallets/werkzeug/releases/tag/3.1.4

https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2