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CVE-2025-66221

5.3 · MEDIUM

Werkzeug is a comprehensive WSGI web application library.

Published Nov 29, 2025CWE-67EPSS 0.51%

Overview

CVE-2025-66221 is a medium-severity vulnerability. It was published on November 29, 2025 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0c13GitHubgithub.com/pallets/werkzeug/releases/tag/3.1.4GitHubgithub.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2

How CyberStrike helps

Frequently asked questions

What is CVE-2025-66221?

CVE-2025-66221 is a medium-severity vulnerability. It was published on November 29, 2025 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2025-66221?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2025-66221?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-66221?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-66221 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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