Improper Handling of Windows Device Names in Werkzeug - CVE-2026-27199
Published: February 23, 2026
Vulnerability identifier: #VU123124
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-27199
CWE-ID: CWE-67
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: The Pallets Projects
Affected software:
Werkzeug
Werkzeug
Detailed vulnerability description
The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.
The vulnerability exists due to the "safe_join" function allows Windows device names as filenames if when preceded by other path segments. A remote attacker can cause reading of the file to hang indefinitely.
How to mitigate CVE-2026-27199
Install updates from vendor's website.