medium6.9
CVE-2025-57804
h2 allows HTTP Request Smuggling due to illegal characters in headers
Impact
### Summary 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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | h2 | < 4.3.0 | 4.3.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/python-hyper/h2/commit/035e9899f95e3709af098f578bfc3cd302298e3a
- https://github.com/python-hyper/h2/security/advisories/GHSA-847f-9342-265h
- https://lists.debian.org/debian-lts-announce/2025/09/msg00004.html
- https://github.com/advisories/GHSA-847f-9342-265h
- https://nvd.nist.gov/vuln/detail/CVE-2025-57804