CVE-2023-23934
LOWCVE-2023-23934 is a low-severity (CVSS 2.6) vulnerability in werkzeug. O3 Security confirms whether CVE-2023-23934 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Wrkzeug's incorrect parsing of nameless cookies leads to __Host- cookies bypass
Blast Radius
werkzeugReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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 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. The issue is fixed in Werkzeug 2.2.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | werkzeug | all versions | 2.2.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for werkzeug. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update werkzeug to 2.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-23934 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2023-23934 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2023-23934. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-23934 in your dependencies?
O3 detects CVE-2023-23934 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.