CVE-2026-69213: Http4s ember core 2.12 Http4s Ember HTTP/2 Has An Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-8f3q-3jmv-7prw",
  "modified" : "2026-09-15T20:00:36Z",
  "published" : "2026-09-15T20:00:36Z",
  "aliases" : [ "CVE-2026-69213" ],
  "summary" : "Http4s Ember HTTP/2 has an unbounded outbound frame queue",
  "details" : "Ember's HTTP/2 connection serializes all outgoing frames through a single unbounded queue drained by one writer fiber (`writeLoop`).  When the write side stalls, any frames the connection keeps producing accumulate in that queue without limit.  The peer can drive this cheaply because the connection emits a control frame in response to inbound frames it does not flow-control: one `PING` ACK per `PING`, one `SETTINGS` ACK per `SETTINGS`, and a `WINDOW_UPDATE` per inbound DATA.  A single unauthenticated connection can therefore exhaust heap and OOM the process.\n\nThis affects an ember server (malicious client) and an ember client (malicious/compromised server that floods the client and stops reading its ACKs).\n\n## Impact\n\nUnauthenticated remote denial of service (OOM) against any ember server built `.withHttp2`, from a single connection, at negligible attacker cost (tiny control frames).  Also affects an ember client talking to a hostile HTTP/2 server.\n\n## Preconditions\n\n- Ember server or client built `.withHttp2`, speaking to a hostile or compromised peer.\n\n## Workarounds\n\n- Disable HTTP/2 (do not call `.withHttp2`).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.http4s:http4s-ember-core_2.12"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.23.35"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.23.34"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.http4s:http4s-ember-core_2.13"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.23.35"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.23.34"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.http4s:http4s-ember-core_3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.23.35"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.23.34"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.http4s:http4s-ember-core_3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.0.0-M1"
      }, {
        "fixed" : "1.0.0-M47"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.0.0-M46"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.http4s:http4s-ember-core_2.13"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.0.0-M1"
      }, {
        "fixed" : "1.0.0-M47"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.0.0-M46"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/http4s/http4s/security/advisories/GHSA-8f3q-3jmv-7prw"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/http4s/http4s/commit/13fe24d6440bde2f1eb70121486cf59c278e6bae"
  }, {
    "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-15T20:00:36Z",
    "nvd_published_at" : null
  }
}