{"id":"CVE-2026-69209","aliases":["GHSA-jrxx-w2m8-5hf5"],"url":"https://o3.security/vulnerability/CVE-2026-69209","summary":"Http4s: WebSocket decoder accepts unbounded message sizes","details":"Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The shared WebSocket decoder permits unbounded message buffering because defragmentation accumulates fragments without a limit and FrameTranscoder accepts declared lengths up to Int.MaxValue. A remote client that completes a WebSocket handshake against an http4s-blaze-server or http4s-ember-server endpoint can exhaust server memory with oversized frames or fragmented messages. The patched decoder applies a configurable 64 MiB default limit to individual frames and defragmented messages through EmberServerBuilder.withMaxWebSocketMessageSize. This issue is fixed in versions 0.23.35 and 1.0.0-M47.","published":"2026-09-15T18:55:29.782Z","modified":"2026-09-16T03:47:20.585207434Z","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":[],"fix":{"url":"https://github.com/http4s/http4s/commit/d578c3c9da6193627d40fa785e612cda7fcd77b3","label":"http4s/http4s@d578c3c"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/69xxx/CVE-2026-69209.json"},{"type":"FIX","url":"https://github.com/http4s/http4s/commit/d578c3c9da6193627d40fa785e612cda7fcd77b3"},{"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/http4s/http4s/security/advisories/GHSA-jrxx-w2m8-5hf5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-69209"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-16T03:47:20.585207434Z"}}