Improper Handling of Windows Device Names Affecting werkzeug package, versions [,3.1.6)
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.
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Test your applications- Snyk IDSNYK-PYTHON-WERKZEUG-15322677
- published20 Feb 2026
- disclosed19 Feb 2026
- creditAli Sherif
Introduced: 19 Feb 2026
CVE-2026-27199 (opens in a new tab)How to fix?
Upgrade werkzeug to version 3.1.6 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.
Notes:
This is only vulnerable on Windows, where special device names are implicitly present in every directory;
This is a bypass of CVE-2025-66221, as the added filtering failed to account for the fact that
safe_joinaccepts paths with multiple segments, such asexample/NUL.