{"id":"CVE-2026-84380","state":"PUBLISHED","title":"HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated","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.","publishedAt":"2026-09-02T17:58:55.520Z","updatedAt":"2026-09-02T18:07:36.980Z","severity":{"score":5.6,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["pydantic httpx2"],"affected":[{"vendor":"pydantic","product":"httpx2","versions":[{"version":"< 2.11.0","status":"affected"}]}],"references":["https://github.com/pydantic/httpx2/security/advisories/GHSA-pf96-p4fj-6566","https://github.com/pydantic/httpx2/pull/1137","https://github.com/pydantic/httpx2/commit/829b93a2393212996f613e635261f777d9ec6eab","https://github.com/pydantic/httpx2/releases/tag/v2.11.0"],"weaknesses":["CWE-444"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/84xxx/CVE-2026-84380.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-84380","state":"PUBLISHED","datePublished":"2026-09-02T17:58:55.520Z","dateUpdated":"2026-09-02T18:07:36.980Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-09-01T16:27:58.130Z"},"containers":{"cna":{"title":"HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"pydantic","product":"httpx2","versions":[{"version":"< 2.11.0","status":"affected"}]}],"references":[{"url":"https://github.com/pydantic/httpx2/security/advisories/GHSA-pf96-p4fj-6566","name":"https://github.com/pydantic/httpx2/security/advisories/GHSA-pf96-p4fj-6566","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/pydantic/httpx2/pull/1137","name":"https://github.com/pydantic/httpx2/pull/1137","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/httpx2/commit/829b93a2393212996f613e635261f777d9ec6eab","name":"https://github.com/pydantic/httpx2/commit/829b93a2393212996f613e635261f777d9ec6eab","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/httpx2/releases/tag/v2.11.0","name":"https://github.com/pydantic/httpx2/releases/tag/v2.11.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":5.6,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-444","lang":"en","description":"CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-02T17:58:55.520Z"},"source":{"advisory":"GHSA-pf96-p4fj-6566","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-02T18:07:09.850518Z","id":"CVE-2026-84380","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-02T18:07:36.980Z"}}]}}}