CVE-2026-27199

Werkzeug is a comprehensive WSGI web application library. Versions 3.1.5 and below, the safe_join function allows Windows device names as filenames if preceded by other path segments. This was previously reported as GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that safe_join accepts paths with multiple segments, such as example/NUL. The function 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 fixed in version 3.1.6.

CVSS v3 5.3 MEDIUM

5.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 3.9 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d	Patch
https://github.com/pallets/werkzeug/releases/tag/3.1.6	Release Notes
https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:palletsprojects:werkzeug:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-02-21 06:17

Updated : 2026-03-03 17:30

NVD link : CVE-2026-27199

Mitre link : CVE-2026-27199

CVE.ORG link : CVE-2026-27199

JSON object : View

Products Affected

palletsprojects

werkzeug

CWE

CWE-67

Improper Handling of Windows Device Names

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