Werkzeug WSGI Improper Handling of Windows Device Names Vulnerability - CVE-2026-21860

Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.5 Werkzeug39s safe_join function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows there are special device names such as CON AUX etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension such as CON.txt or trailing spaces such as CON. This issue has been patched in version 3.1.5.