CVE-2026-21860CWE-67

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

Medium · published January 8, 2026

CVSS v4.0
6.3
EPSS
0%
Percentile
39.9
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
6.3 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
EPSS
0.00482 · 39.9th percentile
Weakness
CWE-67 · Improper Handling of Windows Device Names
Published
2026-01-08T18:34Z
EPSS history
Timeline
  • 08 JAN 18:34Z
    Werkzeug safe_join() allows Windows special device names with compound extensions
    cvelistv5