Vulnerability Description
HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, Request._prepare() in src/httpx2/httpx2/_models.py can add a body-derived Content-Length header to a request that already contains a caller-supplied Transfer-Encoding header because its setdefault() processing checks each default header independently rather than treating the two framing headers as mutually exclusive. Fixed-size byte, JSON, form, and known-length multipart bodies can therefore be serialized over HTTP/1.1 with both headers, allowing request smuggling or connection desynchronization when downstream intermediaries disagree about which framing header takes precedence. This issue is fixed in version 2.11.0.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/pydantic/httpx2/commit/829b93a2393212996f613e635261f777d9ec6e
- https://github.com/pydantic/httpx2/pull/1137
- https://github.com/pydantic/httpx2/releases/tag/v2.11.0
- https://github.com/pydantic/httpx2/security/advisories/GHSA-pf96-p4fj-6566
FAQ
What is CVE-2026-84380?
CVE-2026-84380 is a vulnerability with a CVSS score of 5.6 (MEDIUM). HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, Request._prepare() in src/httpx2/httpx2/_models.py can add a body-derived Content-Length header to a request that already contains ...
How severe is CVE-2026-84380?
CVE-2026-84380 has been rated MEDIUM with a CVSS base score of 5.6/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-84380?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.