CVE-2026-27199: pallets werkzeug

Vulnerability summary

CVE-2026-27199 is a medium (CVSS 6.3) vulnerability in pallets werkzeug. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 45.1% of scored vulnerabilities.

Timeline

1. 21-02-2026
   PublishedVulnerability first disclosed.
2. 24-02-2026
   Last modifiedVulnerability information updated.

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.

• CWE-67Improper Handling of Windows Device NamesThe product constructs pathnames from user input, but it does not handle or incorrectly handles a pathname containing a Windows device name such as AUX or CON. This typically leads to denial of service or an information exposure when the application attempts to process the pathname as a regular file.