CVE-2026-27199

5.3 MEDIUM
Published: February 21, 2026 Modified: March 03, 2026
View on NVD

Description

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/pallets/werkzeug/releases/tag/3.1.6
Source: security-advisories@github.com
Release Notes
https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
Source: security-advisories@github.com
Vendor Advisory

3 reference(s) from NVD

Quick Stats

CVSS v3 Score
5.3 / 10.0
EPSS (Exploit Probability)
0.1%
20th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

palletsprojects