CVE-2025-66221 - CVE House
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Status published Medium CVE-2025-66221

Werkzeug safe_join() allows Windows special device names

Vulnerability Description

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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

References

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Affected Vendor

Affected Software

werkzeug
Vulnerable Versions:
< 3.1.4

Timeline

Official Publish: November 29th, 2025
Last Modified: December 1st, 2025
Added to House: July 22nd, 2026

CVSS Vectors

Weaknesses (CWE)

CWE-67

MITRE ATT&CK TTPs

No associated TTPs found for this vulnerability.