{"id":"CVE-2026-69204","aliases":["GHSA-8h4c-x2wg-6xp8"],"url":"https://o3.security/vulnerability/CVE-2026-69204","summary":"Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)","details":"## Summary\n\nEmber's HTTP/1.1 request parser does not reject a message that carries both a\n`Transfer-Encoding` and a `Content-Length` header. RFC 9112 §6.1 requires a\nserver to treat such a message as a framing error and close the connection.\nAn intermediary that follows the RFC's CL-strip-and-forward path (or that\nprioritises `Content-Length`) will frame the body differently from Ember,\nenabling HTTP request smuggling (CL.TE).\n\n## Impact\n\n### Server\n\nRequest smuggling when ember-server is an origin behind an intermediary that\nforwards both headers over a keep-alive backend connection and frames by\n`Content-Length` while Ember frames by chunked:\n\n- Front-end security bypass: the smuggled request reaches paths the\n  intermediary's ACL/auth layer would have blocked, with attacker-chosen\n  method and headers.\n- Cross-user request hijack: a dangling smuggled prefix concatenates with the\n  next victim's request on the shared backend socket, capturing its headers.\n- Cache poisoning: the smuggled response is associated with the next request\n  key in a caching proxy.\n\n### Client\n\nember-client shares the same parser on the response path. An upstream that\nsends both headers can desync a pooled client connection. This requires a\nmalicious or compromised upstream.\n\n## Preconditions\n\n- Unauthenticated remote attacker (server)\n- ember-server as origin behind a keep-alive intermediary\n- Intermediary forwards a request carrying both `Transfer-Encoding` and\n  `Content-Length` (RFC says it MAY reject; many forward) and frames by\n  `Content-Length`\n- Malicious or compromised upstream (client)\n\n## Workarounds\n\n- Intermediary strictly rejects requests carrying both `Transfer-Encoding`\n  and `Content-Length`\n- Intermediary buffers and re-encodes request bodies\n- Disable backend keep-alive between the intermediary and Ember","published":"2026-09-15T18:43:14.850Z","modified":"2026-10-28T02:31:13.136120428Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Maven","name":"org.http4s:http4s-ember-core_2.12","fixedVersion":"0.23.35"},{"ecosystem":"Maven","name":"org.http4s:http4s-ember-core_2.13","fixedVersion":"0.23.35"},{"ecosystem":"Maven","name":"org.http4s:http4s-ember-core_3","fixedVersion":"0.23.35"},{"ecosystem":"Maven","name":"org.http4s:http4s-ember-core_2.13","fixedVersion":"1.0.0-M47"},{"ecosystem":"Maven","name":"org.http4s:http4s-ember-core_3","fixedVersion":"1.0.0-M47"}],"fix":{"url":"https://github.com/http4s/http4s/commit/9feaf8677951a52af906ae9664ff6f0543d9d810","label":"http4s/http4s@9feaf86"},"references":[{"type":"WEB","url":"https://github.com/http4s/http4s/releases/tag/v0.23.35"},{"type":"WEB","url":"https://github.com/http4s/http4s/releases/tag/v1.0.0-M47"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/69xxx/CVE-2026-69204.json"},{"type":"ADVISORY","url":"https://github.com/http4s/http4s/security/advisories/GHSA-8h4c-x2wg-6xp8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-69204"},{"type":"FIX","url":"https://github.com/http4s/http4s/commit/9feaf8677951a52af906ae9664ff6f0543d9d810"},{"type":"PACKAGE","url":"https://github.com/http4s/http4s"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:31:13.136120428Z"}}