CVE-2025-66221

Werkzeug safe_join() allows Windows special device names

Published: Nov 29, 2025Updated: Dec 3, 2025 Sources: CVE List NVD GHSACWE-67

5.3MEDIUM

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:NConfidentiality

None

I:NIntegrity

None

A:LAvailability

Low

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Weaknesses

CWE-67

Affected Products

palletsprojects

oss-project·US

werkzeugLibrary

package-ecosystem

oss-project·US

werkzeugLibrary

OSS Libraries / pypi

Exploitability

Official Patch Available

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References

https://github.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0c13

github.com

https://github.com/pallets/werkzeug/releases/tag/3.1.4

github.com

https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2

github.com

and 2 more references View all →

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