CVE-2025-66221

low-risk
Published 2025-11-29

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.

Do I need to act?

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0.03% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
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Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
5
CVSS 5.3/10 Medium
NETWORK / LOW complexity

Affected Products (1)

Affected Vendors

Palletsprojects

References (3)

Patch https://github.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0...
Release Notes https://github.com/pallets/werkzeug/releases/tag/3.1.4
Vendor Advisory https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2
26
/ 100
low-risk
Severity 21/34 · High
Exploitability 0/34 · Minimal
Exposure 5/34 · Minimal