{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "4.2.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "8cfb02c547740e16dbfe7aba77bad84b297cec2c"
            }
          ],
          "repo": "https://github.com/python-hyper/hpack",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-8v8h-hg4w-mvq2"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-400"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59980.json"
  },
  "details": "hpack is an HTTP/2 Header Encoding for Python. Prior to version 4.2.0, unbounded variable integer decoding can cause run-away computation on malformed input leading to O(n^2) runtime, effectively blocking further processing with large enough unsanitized input. A fix is available in python-hyper/hpack v4.2.0 to restricted variable integer decoding to uint32 to prevent run-away computation. As a workaround, sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.",
  "id": "CVE-2026-59980",
  "modified": "2026-09-26T03:31:02.193969083Z",
  "published": "2026-09-23T22:07:35.095Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a"
    },
    {
      "type": "WEB",
      "url": "https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59980.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59980"
    },
    {
      "type": "FIX",
      "url": "https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "hpack: Unbounded variable integer decoding can cause run-away computation on malformed input"
}