CVE-2025-66221 — Improper Handling of Windows Device Names in Werkzeug

CWE-67 — Improper Handling of Windows Device Names8 documents7 sources

Severity

6.3MEDIUMNVD

EPSS

0.0%

top 90.88%

CISA KEV

Not in KEV

Exploit

No known exploits

Affected products

Pallets Werkzeug Palletsprojects Werkzeug

Timeline

PublishedNov 29

Latest updateDec 2

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…

CVSS 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

Affected Packages3 packages

▶CVEListV5pallets/werkzeug< 3.1.4

▶NVDpalletsprojects/werkzeug< 3.1.4

▶PyPIpalletsprojects/werkzeug< 3.1.4

Patches

Patch: github.com ↗

🔴Vulnerability Details

GHSA

Werkzeug safe_join() allows Windows special device names↗2025-12-02

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OSV

Werkzeug safe_join() allows Windows special device names↗2025-12-02

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OSV

CVE-2025-66221: Werkzeug is a comprehensive WSGI web application library↗2025-11-29

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CVEList

Werkzeug safe_join() allows Windows special device names↗2025-11-29

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📋Vendor Advisories

Red Hat

Werkzeug: Werkzeug: Denial of service via Windows device names in path segments↗2025-11-29

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Microsoft

Werkzeug safe_join() allows Windows special device names↗2025-11-11

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Debian

CVE-2025-66221: python-werkzeug - Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.4...↗2025

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