{"id":"CVE-2026-84380","summary":"HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated","details":"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.","aliases":["GHSA-pf96-p4fj-6566"],"modified":"2026-09-04T03:47:27.315803138Z","published":"2026-09-02T17:58:55.520Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84380.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-444"]},"references":[{"type":"WEB","url":"https://github.com/pydantic/httpx2/releases/tag/v2.11.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84380.json"},{"type":"ADVISORY","url":"https://github.com/pydantic/httpx2/security/advisories/GHSA-pf96-p4fj-6566"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84380"},{"type":"FIX","url":"https://github.com/pydantic/httpx2/commit/829b93a2393212996f613e635261f777d9ec6eab"},{"type":"FIX","url":"https://github.com/pydantic/httpx2/pull/1137"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/pydantic/httpx2","events":[{"introduced":"0"},{"fixed":"829b93a2393212996f613e635261f777d9ec6eab"},{"fixed":"2b13fa92e4181d5e0f56772205360b2aa12f109d"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"2.11.0"}]}}],"versions":["v2.10.0","v2.9.1","v2.9.0","v2.8.0","v2.7.0","v2.6.0","v2.5.0","v2.4.0","v2.3.0","v2.2.0","v2.1.0","v2.0.0","v2.0.0b1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-84380.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L"}]}