{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2026-54556",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-54556",
    "idYear": 2026,
    "status": "PUBLISHED",
    "publishedAt": "2026-08-26T14:10:22.349Z",
    "updatedAt": "2026-08-29T02:38:44.725Z",
    "importedAt": "2026-10-24T01:58:20.586Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "Http4s: HTTP/2 Denial of Service with Ember Backend",
      "summary": "Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala concatenates HEADERS and CONTINUATION frame fragments and decodes them into a single List, but maxHeaderSize accounting does not include indexed headers or HPACK per-header overhead. A small compressed header block can therefore expand into a much larger decoded representation that remains in memory for processing. Servers exposed to untrusted HTTP/2 traffic and clients directed to an untrusted HTTP/2 server are affected, and concurrent malicious connections can exhaust the process heap. This issue is fixed in versions 0.23.35 and 1.0.0-M47.",
      "affected": [
        {
          "vendor": "http4s",
          "product": "http4s",
          "versions": [
            {
              "version": "< 0.23.35",
              "status": "affected"
            },
            {
              "version": ">= 1.0.0-M1, < 1.0.0-M46",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "org.http4s",
          "product": "http4s-ember-core_2.12",
          "versions": [
            {
              "version": "< 0.23.35",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "org.http4s",
          "product": "http4s-ember-core_2.13",
          "versions": [
            {
              "version": ">= 1.0.0-M1, < 1.0.0-M46",
              "status": "affected"
            },
            {
              "version": "< 0.23.35",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "org.http4s",
          "product": "http4s-ember-core_3",
          "versions": [
            {
              "version": ">= 1.0.0-M1, < 1.0.0-M46",
              "status": "affected"
            },
            {
              "version": "< 0.23.35",
              "status": "affected"
            }
          ]
        }
      ]
    }
  }
}