CVE-2023-23934 — Werkzeug is a comprehensive WSGI web application library

Werkzeug is a comprehensive WSGI web application library. 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 `=__Hos

01What is this vulnerability?

Werkzeug is a comprehensive WSGI web application library. 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 prior to 2.2.3 will parse the cookie `=__Host-test=bad` as __Host-test=bad`. If a…

02Affected products

Vendor	Product	Versions
pallets	werkzeug	< 2.2.3

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-02-14T19:56:22.659Z
• Last modified: 2025-03-10T21:11:36.910Z

09References

• github.com — https://github.com/pallets/werkzeug/security/advisories/GHSA-px8h-6qxv-m22q
• github.com — https://github.com/pallets/werkzeug/commit/cf275f42acad1b5950c50ffe8ef58fe62cdce…
• github.com — https://github.com/pallets/werkzeug/releases/tag/2.2.3
• www.debian.org — https://www.debian.org/security/2023/dsa-5470
• security.netapp.com — https://security.netapp.com/advisory/ntap-20230818-0003/