Vulnerability Description
h2 is a pure-Python implementation of a HTTP/2 protocol stack. Prior to version 4.3.0, an HTTP/2 request splitting vulnerability allows attackers to perform request smuggling attacks by injecting CRLF characters into headers. This occurs when servers downgrade HTTP/2 requests to HTTP/1.1 without properly validating header names/values, enabling attackers to manipulate request boundaries and bypass security controls. This issue has been patched in version 4.3.0.
Related Weaknesses (CWE)
References
- https://github.com/python-hyper/h2/commit/035e9899f95e3709af098f578bfc3cd302298e
- https://github.com/python-hyper/h2/security/advisories/GHSA-847f-9342-265h
- https://lists.debian.org/debian-lts-announce/2025/09/msg00004.html
FAQ
What is CVE-2025-57804?
CVE-2025-57804 is a documented vulnerability. h2 is a pure-Python implementation of a HTTP/2 protocol stack. Prior to version 4.3.0, an HTTP/2 request splitting vulnerability allows attackers to perform request smuggling attacks by injecting CRLF...
How severe is CVE-2025-57804?
CVSS scoring is not yet available for CVE-2025-57804. Check NVD for updates.
Is there a patch for CVE-2025-57804?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.