Improper Handling of Windows Device Names Affecting werkzeug package, versions [,3.1.4)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-PYTHON-WERKZEUG-14151620
- published30 Nov 2025
- disclosed29 Nov 2025
- creditOblivionsage
Introduced: 29 Nov 2025
NewCVE-2025-66221 (opens in a new tab)How to fix?
Upgrade werkzeug to version 3.1.4 or higher.
Overview
Affected versions of this package are vulnerable to Improper Handling of Windows Device Names via the safe_join function. An attacker can cause the application to hang indefinitely by requesting a path ending with a Windows special device name, e.g. CON or NUL.
Note: This is only vulnerable on Windows, where special device names are implicitly present in every directory.