Incorrect parsing of nameless cookies leads to __Host- cookies bypassGHSA-px8h-6qxv-m22q
LOWFix: pallets/werkzeug@cf275f4GHSA-px8h-6qxv-m22q is a low-severity (CVSS 2.6) Improper Input Validation vulnerability in werkzeug. A fix is available for werkzeug — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-px8h-6qxv-m22q.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
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 | 2.2.3pip install --upgrade 'werkzeug==2.2.3' |
Affected Products
werkzeugpalletsprojectsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for werkzeug, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update werkzeug to 2.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-px8h-6qxv-m22q 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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ceph Storage 7.1 | oath-toolkit-0:2.6.12-1.el8cp | RHSA-2025:4664 |
| Red Hat Ceph Storage 8.1 | oath-toolkit-0:2.6.12-1.el9cp | RHSA-2025:9775 |
| Red Hat OpenStack Platform 17.0 | python-werkzeug-0:2.0.1-5.el9ost | RHSA-2023:1018 |
Frequently Asked Questions
Is GHSA-px8h-6qxv-m22q in your dependencies?
Find it across PyPI, including transitive dependencies.