Security advisory

{
  "id": "cbf0d299c4a640f5a05c8ab18229f40c5e1a1e59b976d14a84dc05a5baea4ea3",
  "url": "https://osv.dev/vulnerability/CVE-2016-6581",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2016-6581",
    "summary": "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.",
    "evidence": "osv:CVE-2016-6581",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2016-6581",
      "aliases": [
        "CVE-2016-6581",
        "GHSA-ffq8-576r-v26g",
        "PYSEC-2017-87"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/python-hyper/hpack",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fc618368a4b0c56a6bcce776787fc21cacbb5b10"
                },
                {
                  "last_affected": "ab9e9a65a6be582b33dae280b87daba269377f98"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:python:hpack:1.0:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "1.0"
                      },
                      {
                        "last_affected": "1.0"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "cpe": "cpe:2.3:a:python:hpack:2.0:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.0"
                      },
                      {
                        "last_affected": "2.0"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "cpe": "cpe:2.3:a:python:hpack:2.0.1:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.0.1"
                      },
                      {
                        "last_affected": "2.0.1"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "cpe": "cpe:2.3:a:python:hpack:2.1.1:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.1.1"
                      },
                      {
                        "last_affected": "2.1.1"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "cpe": "cpe:2.3:a:python:hpack:2.2:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.2"
                      },
                      {
                        "last_affected": "2.2"
                      }
                    ],
                    "source": "CPE_STRING"
                  }
                ]
              }
            }
          ],
          "versions": [
            "1.0",
            "2.0",
            "2.0.1",
            "2.1.1",
            "2.2",
            "v2.2.0",
            "v2.1.1",
            "v2.1.0",
            "v2.0.1",
            "v2.0.0",
            "v1.1.0",
            "v1.0.1",
            "v1.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2016-6581.json"
          }
        }
      ],
      "modified": "2026-10-24T10:30:58.406113051Z",
      "provider": "osv",
      "references": [
        "https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html"
      ],
      "provider_metadata": {
        "unresolved_ranges": [
          {
            "cpes": [
              "cpe:2.3:a:python:hyper:0.4:*:*:*:*:*:*:*",
              "cpe:2.3:a:python:hyper:0.6:*:*:*:*:*:*:*"
            ],
            "vendor_product": "python:hyper",
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "0.4"
                  },
                  {
                    "last_affected": "0.4"
                  },
                  {
                    "introduced": "0.6"
                  },
                  {
                    "last_affected": "0.6"
                  }
                ],
                "source": "CPE_STRING"
              }
            ]
          }
        ]
      }
    },
    "related_cves": [
      {
        "value": "CVE-2016-6581",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 439087,
  "published_at": "2017-01-10T15:59:00.423+00:00"
}