Improper Handling of Windows Device Names Affecting werkzeug package, versions [,3.1.5)
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-14908843
- published9 Jan 2026
- disclosed8 Jan 2026
- creditYue (Knox) Liu, Omar M. Hasan
Introduced: 8 Jan 2026
CVE-2026-21860 (opens in a new tab)How to fix?
Upgrade werkzeug to version 3.1.5 or higher.
Overview
Affected versions of this package are vulnerable to Improper Handling of Windows Device Names via the safe_join() function, which permits path segments containing Windows special device names with file extensions or trailing spaces. An attacker can access unintended files or devices by crafting malicious path inputs.
Note:
This issues exists due to the incomplete fix for CVE-2025-66221 that failed to account for compound extensions such as CON.txt.html or trailing spaces.