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Moderate severityOSV Advisory· Published Jan 8, 2026· Updated Jan 8, 2026

Werkzeug safe_join() allows Windows special device names with compound extensions

CVE-2026-21860

Description

Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.5, Werkzeug's safe_join function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows, there are special device names such as CON, AUX, etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension, such as CON.txt, or trailing spaces such as CON. This issue has been patched in version 3.1.5.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
WerkzeugPyPI
< 3.1.53.1.5

Affected products

23

Patches

Vulnerability mechanics

References

4

News mentions

0

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