GHSA-VMM3-XGCX-67HM高危已审查

http4s has HTTP/2 Denial of Service with Ember Backend

OSV 1.4.0 · github-reviewed · 修改于 2026-08-26 22:10

发布时间

2026-08-26 22:10

GitHub 审查时间

2026-08-26 22:10

NVD 发布时间

—

源文件

advisories/github-reviewed/2026/08/GHSA-vmm3-xgcx-67hm/GHSA-vmm3-xgcx-67hm.json

公告说明

Summary

http4s 0.23.x and 1.0 servers running ember with http2 enabled are vulnerable to a denial of service attack using a HPACK bomb vulnerability recently disclosed as affecting other http2 servers.

Impact

Denial of Service:

Affects any http4s server running the ember backend with HTTP/2 enabled that is exposed to untrusted traffic.
Affects any http4s client running the ember backend with HTTP/2 enabled that can be directed to an untrusted server.

Details

The issue occurs in the Hpack wrapper. Ember concatenates the header and continuation frames before decoding all headers at once. When the code decodes the attack payload, the relatively small packets decode to a significantly larger amount of data which is returned as a single List which is then held in memory for further processing. With enough concurrent connections (~5 with a 2GB heap in testing) this leads to an OOM, eg:

java.lang.OutOfMemoryError: Java heap space
        at scala.collection.mutable.ListBuffer.scala$collection$mutable$ListBuffer$$freshFrom(ListBuffer.scala:129)
        at scala.collection.mutable.ListBuffer.addAll(ListBuffer.scala:147)
        at scala.collection.mutable.ListBuffer.addAll(ListBuffer.scala:40)
        at scala.collection.mutable.Growable.$plus$plus$eq(Growable.scala:69)
        at scala.collection.mutable.Growable.$plus$plus$eq$(Growable.scala:69)
        at scala.collection.mutable.AbstractBuffer.$plus$plus$eq(Buffer.scala:314)
        at org.http4s.Header$.org$http4s$Header$ToRaw$$anon$10$$_$$lessinit$greater$$anonfun$2(Header.scala:192)
        at org.http4s.Header$ToRaw$$anon$10$$Lambda/0x00001fe001239c50.apply(Unknown Source)
        at scala.collection.immutable.List.foreach(List.scala:334)
        at org.http4s.Header$ToRaw$$anon$10.<init>(Header.scala:192)
        at org.http4s.Header$ToRaw$.scalaCollectionSeqToRaw(Header.scala:195)
        at org.http4s.Headers$.apply(Headers.scala:220)
        at org.http4s.ember.core.h2.PseudoHeaders$.headersToRequestNoBody(PseudoHeaders.scala:95)
        at org.http4s.ember.core.h2.H2Stream.receiveHeaders$$anonfun$1$$anonfun$2$$anonfun$3$$anonfun$2(H2Stream.scala:248)
        at org.http4s.ember.core.h2.H2Stream$$Lambda/0x00001fe001511fd8.apply(Unknown Source)
        at cats.effect.IOFiber.runLoop(IOFiber.scala:429)
        at cats.effect.IOFiber.autoCedeR(IOFiber.scala:1460)
        at cats.effect.IOFiber.run(IOFiber.scala:129)
        at cats.effect.unsafe.WorkerThread.run(WorkerThread.scala:935)

标识信息

别名 / CVE

CVE-2026-54556

CWE

CWE-409

软件生态

Maven

扩展资料

暂无扩展资料。

CVSS 评分

CVSS_V4

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

原始 OSV JSON

{
  "id": "GHSA-vmm3-xgcx-67hm",
  "aliases": [
    "CVE-2026-54556"
  ],
  "details": "### Summary\n\nhttp4s 0.23.x and 1.0 servers running ember with http2 enabled are vulnerable to a denial of service attack using a HPACK bomb vulnerability recently disclosed as affecting other http2 servers.\n\n### Impact\n\nDenial of Service:\n- Affects any http4s server running the ember backend with HTTP/2 enabled that is exposed to untrusted traffic.\n- Affects any http4s client running the ember backend with HTTP/2 enabled that can be directed to an untrusted server.\n\n### Details\n\nThe issue occurs in the [Hpack wrapper](https://github.com/http4s/http4s/blob/c63fbff43dfe7e3bec25b789fd0a0027ec40ed62/ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala#L54). Ember concatenates the header and continuation frames before decoding all headers at once. When the code decodes the attack payload, the relatively small packets decode to a significantly larger amount of data which is returned as a single List which is then held in memory for further processing. With enough concurrent connections (~5 with a 2GB heap in testing) this leads to an OOM, eg:\n\n```\njava.lang.OutOfMemoryError: Java heap space\n        at scala.collection.mutable.ListBuffer.scala$collection$mutable$ListBuffer$$freshFrom(ListBuffer.scala:129)\n        at scala.collection.mutable.ListBuffer.addAll(ListBuffer.scala:147)\n        at scala.collection.mutable.ListBuffer.addAll(ListBuffer.scala:40)\n        at scala.collection.mutable.Growable.$plus$plus$eq(Growable.scala:69)\n        at scala.collection.mutable.Growable.$plus$plus$eq$(Growable.scala:69)\n        at scala.collection.mutable.AbstractBuffer.$plus$plus$eq(Buffer.scala:314)\n        at org.http4s.Header$.org$http4s$Header$ToRaw$$anon$10$$_$$lessinit$greater$$anonfun$2(Header.scala:192)\n        at org.http4s.Header$ToRaw$$anon$10$$Lambda/0x00001fe001239c50.apply(Unknown Source)\n        at scala.collection.immutable.List.foreach(List.scala:334)\n        at org.http4s.Header$ToRaw$$anon$10.<init>(Header.scala:192)\n        at org.http4s.Header$ToRaw$.scalaCollectionSeqToRaw(Header.scala:195)\n        at org.http4s.Headers$.apply(Headers.scala:220)\n        at org.http4s.ember.core.h2.PseudoHeaders$.headersToRequestNoBody(PseudoHeaders.scala:95)\n        at org.http4s.ember.core.h2.H2Stream.receiveHeaders$$anonfun$1$$anonfun$2$$anonfun$3$$anonfun$2(H2Stream.scala:248)\n        at org.http4s.ember.core.h2.H2Stream$$Lambda/0x00001fe001511fd8.apply(Unknown Source)\n        at cats.effect.IOFiber.runLoop(IOFiber.scala:429)\n        at cats.effect.IOFiber.autoCedeR(IOFiber.scala:1460)\n        at cats.effect.IOFiber.run(IOFiber.scala:129)\n        at cats.effect.unsafe.WorkerThread.run(WorkerThread.scala:935)\n```\n\n### Fix\n  \nThe Hpack handling code has a configurable max header size parameter, but it does not include indexed headers in that accounting, allowing the attack to bypass the limit. There is not any configuration available in current http4s versions that can be enabled to prevent this attack short of disabling http2.\n\nA fix has been tested locally that threads the maxHeaderSize setting from the server builder into the Hpack code. Using this, connections can be prematurely terminated once the decoded data size exceeds the maxHeaderSize that users can already configure.\n\n### Workarounds\n\nIf you can't upgrade immediately:\n- Disable HTTP/2 in Ember backends",
  "summary": "http4s has HTTP/2 Denial of Service with Ember Backend",
  "affected": [
    {
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ]
        }
      ],
      "package": {
        "name": "org.http4s:http4s-ember-core_2.12",
        "ecosystem": "Maven"
      },
      "database_specific": {
        "last_known_affected_version_range": "<= 0.23.34"
      }
    },
    {
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ]
        }
      ],
      "package": {
        "name": "org.http4s:http4s-ember-core_2.13",
        "ecosystem": "Maven"
      },
      "database_specific": {
        "last_known_affected_version_range": "< 1.0.0-M46"
      }
    },
    {
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ]
        }
      ],
      "package": {
        "name": "org.http4s:http4s-ember-core_3",
        "ecosystem": "Maven"
      },
      "database_specific": {
        "last_known_affected_version_range": "<= 0.23.34"
      }
    },
    {
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ]
        }
      ],
      "package": {
        "name": "org.http4s:http4s-ember-core_3",
        "ecosystem": "Maven"
      },
      "database_specific": {
        "last_known_affected_version_range": "< 1.0.0-M46"
      }
    },
    {
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ]
        }
      ],
      "package": {
        "name": "org.http4s:http4s-ember-core_2.13",
        "ecosystem": "Maven"
      },
      "database_specific": {
        "last_known_affected_version_range": "<= 0.23.34"
      }
    }
  ],
  "modified": "2026-08-26T14:10:59Z",
  "severity": [
    {
      "type": "CVSS_V4",
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
    }
  ],
  "published": "2026-08-26T14:10:59Z",
  "references": [
    {
      "url": "https://github.com/http4s/http4s/security/advisories/GHSA-vmm3-xgcx-67hm",
      "type": "WEB"
    },
    {
      "url": "https://github.com/http4s/http4s/commit/6e8eccd64a6a74ab4811897881e95e0e1b3a818e",
      "type": "WEB"
    },
    {
      "url": "https://github.com/http4s/http4s",
      "type": "PACKAGE"
    },
    {
      "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": "WEB"
    }
  ],
  "schema_version": "1.4.0",
  "database_specific": {
    "cwe_ids": [
      "CWE-409"
    ],
    "severity": "HIGH",
    "github_reviewed": true,
    "nvd_published_at": null,
    "github_reviewed_at": "2026-08-26T14:10:59Z"
  }
}