GHSA-9VWC-PC8P-253Q

Vulnerability from github – Published: 2026-09-15 19:53 – Updated: 2026-09-15 19:53
VLAI
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.

Impact

Unauthenticated 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).

The 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.

Preconditions

  • Server: with .withHttp2 enabled.
  • Client: makes HTTP/2 requests to malicious or compromised sites. enablePush is not enforced.

Workarounds

  • Disable HTTP/2 on EmberServerBuilder or EmberClientBuilder (default)
  • Client only: avoid HTTP/2 to untrusted servers until patched.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_2.12"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_2.13"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M46"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_2.13"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M46"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-69203"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-15T19:53:14Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "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\u0027s 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.",
  "id": "GHSA-9vwc-pc8p-253q",
  "modified": "2026-09-15T19:53:25Z",
  "published": "2026-09-15T19:53:14Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS"
}



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