CVE-2023-23934Low· 2.6▾ SunlitIncorrect parsing of nameless cookies leads to __Host- cookies bypass
▾ Sunlit zone — Low / medium · no exploitation signal
impact 14.3 · likelihood 0.1 · exploitation 0
Need a working PoC? Pro members can cast a request and our team develops one — it lands right here.
Exploit-prediction probability, daily snapshots since Sep 12.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.5%
Browsers may allow "nameless" cookies that look like =value instead of key=value. A vulnerable browser may allow a compromised application on an adjacent subdomain to exploit this to set a cookie like =__Host-test=bad for another subdomain.
Werkzeug <= 2.2.2 will parse the cookie =__Host-test=bad as __Host-test=bad. If a Werkzeug application is running next to a vulnerable or malicious subdomain which sets such a cookie using a vulnerable browser, the Werkzeug application will see the bad cookie value but the valid cookie key.
werkzeug < 2.2.3Upgrade to a patched release:
werkzeug 2.2.3Connected by shared product, vendor, weakness, or advisory.
CVE-2023-25577High· 7.5High resource usage when parsing multipart form data with many fields
CVE-2023-46136Medium· 5.7Werkzeug DoS: High resource usage when parsing multipart/form-data containing a large part with CR/LF character at the beginning
CVE-2026-27199MediumWerkzeug safe_join() allows Windows special device names
CVE-2024-49767High· 7.5Werkzeug possible resource exhaustion when parsing file data in forms
CVE-2019-14322High· 7.5Pallets Werkzeug vulnerable to Path Traversal
CVE-2025-66221MediumWerkzeug safe_join() allows Windows special device names