{"cve":"CVE-2026-84380","nvd":{"published":"2026-09-02T18:21:29.513","modified":"2026-09-09T21:05:23.237","status":"Awaiting Analysis","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L","score":5.6},"cwes":["CWE-444"],"references":["https://github.com/pydantic/httpx2/commit/829b93a2393212996f613e635261f777d9ec6eab","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"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-84380","score":0.00221,"percentile":0.12727,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-pf96-p4fj-6566","url":"https://osv.dev/vulnerability/GHSA-pf96-p4fj-6566","summary":"HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated","modified":"2026-09-10T12:25:28.219277036Z","packages":[{"ecosystem":"PyPI","name":"httpx2","purl":"pkg:pypi/httpx2","ranges":["<2.11.0"],"fixed":["2.11.0"]}]},{"id":"PYSEC-2026-3849","url":"https://osv.dev/vulnerability/PYSEC-2026-3849","summary":"HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated","modified":"2026-09-10T12:15:06.096986959Z","packages":[{"ecosystem":"PyPI","name":"httpx2","purl":"pkg:pypi/httpx2","ranges":["<2.11.0"],"fixed":["2.11.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}