{"id":"CVE-2026-69203","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-69203","summary":"Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS","details":"An ember server with HTTP/2 enabled (`.withHttp2`) does not enforce `SETTINGS_MAX_CONCURRENT_STREAMS` on streams opened by the peer.  A single unauthenticated connection can open an unbounded number of concurrent streams, each of which allocates per-stream server state that is never released, exhausting the heap.\n\n## Impact\n\nUnauthenticated remote denial of service (memory exhaustion) against any Ember server built `.withHttp2`.  This is the resource-exhaustion class of the HTTP/2 \"Rapid Reset\" family (CVE-2023-44487).\n\nThe same unchecked allocation path is reachable on the client via server-initiated `PUSH_PROMISE` frames, so a malicious or compromised server can exhaust an ember-client's heap the same way.\n\n## Preconditions\n\n- Server: with `.withHttp2` enabled.\n- Client: makes HTTP/2 requests to malicious or compromised sites.  `enablePush` is not enforced.\n\n## Workarounds\n\n- Disable HTTP/2 on `EmberServerBuilder` or `EmberClientBuilder` (default)\n- Client only: avoid HTTP/2 to untrusted servers until patched.","published":"2026-09-15T19:53:14Z","modified":"2026-09-15T20:00:40.544947819Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"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/4983de1f93f2caaa3b9de310cf6a9db32c50d66e","label":"http4s/http4s@4983de1"},"references":[{"type":"WEB","url":"https://github.com/http4s/http4s/security/advisories/GHSA-9vwc-pc8p-253q"},{"type":"WEB","url":"https://github.com/http4s/http4s/commit/4983de1f93f2caaa3b9de310cf6a9db32c50d66e"},{"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-15T20:00:40.544947819Z"}}