CVE-2025-66221CWE-67

Werkzeug safe_join() allows Windows special device names

Medium · published November 29, 2025

CVSS v4.0
6.3
EPSS
1%
Percentile
41.7
In the wild
Unconfirmed
What it is

Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.4, Werkzeug's safe_join function allows path segments with Windows device names. On Windows, there are special device names such as CON, AUX, etc that are implicitly present and readable in every directory. send_from_directory uses safe_join to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely. This issue has been patched in version 3.1.4.

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
0.00511 · 41.7th percentile
Weakness
CWE-67 · Improper Handling of Windows Device Names
Published
2025-11-29T02:28Z
EPSS history
Timeline
  • 29 NOV 02:28Z
    Werkzeug safe_join() allows Windows special device names
    cvelistv5