BREW-HTTPX2-CVE-2016-6581 (GHSA-FFQ8-576R-V26G)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:57 – Updated: 2026-09-10 19:29 – Source website
VLAI
Summary
HPACK Denial of Service vulnerability (HPACK Bomb)
Details

A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targeted for a denial of service attack, specifically a so-called "HPACK Bomb" attack. This attack occurs when an attacker inserts a header field that is exactly the size of the HPACK dynamic header table into the dynamic header table. The attacker can then send a header block that is simply repeated requests to expand that field in the dynamic table. This can lead to a gigantic compression ratio of 4,096 or better, meaning that 16kB of data can decompress to 64MB of data on the target machine.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "hpack",
        "resource_purl": "pkg:pypi/hpack@4.2.0",
        "upstream_fixed_in": "2.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "httpx2",
        "purl": "pkg:brew/httpx2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/hpack@4.2.0",
        "name": "hpack",
        "resource": "hpack",
        "strategy": "registry",
        "subject_version": "4.2.0"
      }
    ]
  },
  "details": "A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targeted for a denial of service attack, specifically a so-called \"HPACK Bomb\" attack. This attack occurs when an attacker inserts a header field that is exactly the size of the HPACK dynamic header table into the dynamic header table. The attacker can then send a header block that is simply repeated requests to expand that field in the dynamic table. This can lead to a gigantic compression ratio of 4,096 or better, meaning that 16kB of data can decompress to 64MB of data on the target machine.",
  "id": "BREW-httpx2-CVE-2016-6581",
  "modified": "2026-09-10T19:29:23Z",
  "published": "2026-08-13T16:57:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2016-6581"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-ffq8-576r-v26g"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/hpack/PYSEC-2017-87.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/python-hyper/hpack"
    },
    {
      "type": "WEB",
      "url": "https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html"
    },
    {
      "type": "WEB",
      "url": "https://web.archive.org/web/20200227233559/http://www.securityfocus.com/bid/92315"
    },
    {
      "type": "WEB",
      "url": "http://python-hyper.org/projects/hpack/en/stable/security/CVE-2016-6581.html"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "HPACK Denial of Service vulnerability (HPACK Bomb)",
  "upstream": [
    "GHSA-ffq8-576r-v26g",
    "CVE-2016-6581",
    "PYSEC-2017-87"
  ]
}



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