CVE-2026-59980

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

• https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a security-advisories@github.com
• https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403 security-advisories@github.com
• https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c security-advisories@github.com
• https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2 security-advisories@github.com

The full cvelistV5 record. Download as CVE-2026-59980.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "hpack",
          "vendor": "python-hyper",
          "versions": [
            {
              "status": "affected",
              "version": "< 4.2.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "CWE-400: Uncontrolled Resource Consumption",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-23T22:07:35.095Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2"
        },
        {
          "name": "https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c"
        },
        {
          "name": "https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a"
        },
        {
          "name": "https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403"
        }
      ],
      "source": {
        "advisory": "GHSA-8v8h-hg4w-mvq2",
        "discovery": "UNKNOWN"
      },
      "title": "hpack: Unbounded variable integer decoding can cause run-away computation on malformed input"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-59980",
    "datePublished": "2026-09-23T22:07:35.095Z",
    "dateReserved": "2026-07-07T19:41:00.004Z",
    "dateUpdated": "2026-09-23T22:07:35.095Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}