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GHSA-6M4X-PP6Q-5JMM

Vulnerability from github – Published: 2026-09-15 19:52 – Updated: 2026-09-15 19:52
VLAI
Summary
Http4s Ember HTTP/2: unbounded inbound body buffering
Details

Ember's HTTP/2 stack replenishes the inbound flow-control window based on bytes received off the wire, not bytes consumed by the application. Received DATA is buffered in an unbounded per-stream channel. Flow control therefore provides no backpressure: a peer can stream a large or unbounded body faster than the application drains it and the connection retains every payload in heap.

This is the read-path mirror of the outbound queue issue.

This affects an Ember receiving a request body and an Ember client receiving a response body from a hostile server.

Impact

Unauthenticated remote denial of service (OOM) against any Ember server built .withHttp2 for a non-draining or slow-draining route, and against an Ember client consuming from a hostile or compromised server.

Workarounds

  • Disable HTTP/2 to remove the vector entirely.
  • Apply an aggregate request-entity size limit (e.g. EntityLimiter middleware) on routes that consume the body.
  • Ensure handlers fully drain request bodies with aggressive idle timeouts.
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
To clipboard 

{
  "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-2026-69202"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-15T19:52:58Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "Ember\u0027s HTTP/2 stack replenishes the inbound flow-control window based on bytes\nreceived off the wire, not bytes consumed by the application.  Received DATA is buffered in an unbounded per-stream channel.  Flow control therefore\nprovides no backpressure: a peer can stream a large or unbounded body faster than the application drains it and the connection retains every payload in heap.\n\nThis is the read-path mirror of the [outbound queue issue](https://github.com/http4s/http4s/security/advisories/GHSA-8f3q-3jmv-7prw).\n\nThis affects an Ember receiving a request body and an Ember client receiving a response body from a hostile server.\n\n### Impact\n\nUnauthenticated remote denial of service (OOM) against any Ember server built\n`.withHttp2` for a non-draining or slow-draining route, and against an Ember client consuming from a hostile or compromised server.\n\n### Workarounds\n\n- Disable HTTP/2 to remove the vector entirely.\n- Apply an aggregate request-entity size limit (e.g. `EntityLimiter` middleware) on routes that consume the body.\n- Ensure handlers fully drain request bodies with aggressive idle timeouts.",
  "id": "GHSA-6m4x-pp6q-5jmm",
  "modified": "2026-09-15T19:52:58Z",
  "published": "2026-09-15T19:52:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/security/advisories/GHSA-6m4x-pp6q-5jmm"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/commit/22d2335975d02dc9fb9fb75cfe002279521d86ac"
    },
    {
      "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: unbounded inbound body buffering"
}



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