{"id":"GHSA-9998-894r-fwvr","summary":"Http4s Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)","details":"## Summary\n\nEmber's HTTP/1.1 header parser matches the `Transfer-Encoding` header value\nwith a case-sensitive substring test (`hValue.contains(\"chunked\")`). RFC\n9112 §7 requires transfer-coding names to be compared case-insensitively. A\nrequest carrying `Transfer-Encoding: Chunked` (capital C) is therefore not\nrecognised as chunked, and Ember falls back to framing by `Content-Length`\n(or zero if absent) while a compliant intermediary frames the same bytes by\nchunked encoding. The two parsers then disagree on where the request body\nends, enabling HTTP request smuggling (TE.CL / TE.0).\n\nThe same line of code admits two further variants:\n\n- The substring test misfires on `Transfer-Encoding: notchunked` (an inverse\n  desync — Ember treats it as chunked while a compliant intermediary\n  rejects the unknown coding).\n- Header field bytes are decoded with the platform-default charset. Under\n  UTF-8 the wire bytes `E2 84 AA` decode to U+212A KELVIN SIGN, which\n  `String.equalsIgnoreCase` Unicode-case-folds to `k`, so\n  `Transfer-Encoding: chun\u003cU+212A\u003eed` matches `chunked` once the comparison\n  is made case-insensitive without also pinning the decode to ISO-8859-1.\n\n## Impact\n\n### Server\n\nRequest smuggling when ember-server is an origin behind an intermediary that\nhonours `Transfer-Encoding` case-insensitively per RFC, forwards the header\nvalue verbatim, and reuses keep-alive connections to the backend:\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 partial smuggled prefix left in Ember's\n  connection buffer is concatenated with the next victim's request on the\n  same pooled backend connection, exposing its headers (e.g. `Cookie`,\n  `Authorization`) to the attacker.\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 `HeaderP.parse` on the response path, enabling\nresponse smuggling when http4s is used as a gateway. This is less severe: it\nrequires a malicious or compromised upstream rather than an anonymous remote\nclient.\n\n## Preconditions\n\n- Unauthenticated remote attacker (server)\n- ember-server as origin behind a keep-alive intermediary\n- Intermediary treats `Transfer-Encoding` case-insensitively (per RFC) and\n  forwards the header value without lowercasing it\n- Malicious or compromised upstream (client)\n\n## Workarounds\n\n- Intermediary fully buffers and re-encodes request bodies (e.g. nginx with\n  default `proxy_request_buffering on`)\n- Intermediary normalises the `Transfer-Encoding` value (lowercases the\n  token) before forwarding\n- Disable backend keep-alive between the intermediary and Ember","aliases":["CVE-2026-69205"],"modified":"2026-09-15T20:00:40.521015729Z","published":"2026-09-15T19:54:25Z","database_specific":{"nvd_published_at":null,"cwe_ids":["CWE-444"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-09-15T19:54:25Z"},"references":[{"type":"WEB","url":"https://github.com/http4s/http4s/security/advisories/GHSA-9998-894r-fwvr"},{"type":"WEB","url":"https://github.com/http4s/http4s/commit/5e88b2e7b4e6ea2f0c61040a4bc9de0d73e51217"},{"type":"PACKAGE","url":"https://github.com/http4s/http4s"},{"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"}],"affected":[{"package":{"name":"org.http4s:http4s-ember-core_3","ecosystem":"Maven","purl":"pkg:maven/org.http4s/http4s-ember-core_3"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.23.35"}]}],"versions":["0.22.0","0.22.0-M8","0.22.0-RC1","0.22.1","0.22.10","0.22.11","0.22.12","0.22.13","0.22.14","0.22.15","0.22.2","0.22.3","0.22.4","0.22.5","0.22.6","0.22.7","0.22.8","0.22.9","0.23.0","0.23.0-M1","0.23.0-RC1","0.23.1","0.23.10","0.23.11","0.23.12","0.23.13","0.23.14","0.23.15","0.23.16","0.23.17","0.23.18","0.23.19","0.23.19-RC1","0.23.19-RC2","0.23.19-RC3","0.23.2","0.23.20","0.23.21","0.23.22","0.23.23","0.23.24","0.23.25","0.23.26","0.23.27","0.23.28","0.23.29","0.23.3","0.23.30","0.23.31","0.23.32","0.23.33","0.23.34","0.23.4","0.23.5","0.23.6","0.23.7","0.23.8","0.23.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-9998-894r-fwvr/GHSA-9998-894r-fwvr.json","last_known_affected_version_range":"\u003c= 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