HTSlib through 1.24 Heap Out-of-Bounds Write via Truncated .gzi Index Count

{
  "id": "092360b6861b09b0247a81971b6031548ef8e605465c29c86d33677a568f2434",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-116742",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "HTSlib through 1.24 Heap Out-of-Bounds Write via Truncated .gzi Index Count",
    "summary": "HTSlib through 1.24 contains a heap out-of-bounds write and read vulnerability in bgzf_index_load_hfile() in bgzf.c that allows attackers to corrupt heap memory by supplying a crafted .gzi index entry count. A count of 0xFFFFFFFF truncates noffs to zero, causing writes past a malloc(0) buffer and an offs[-1] read in bgzf_useek(), resulting in heap corruption or crashes in tools like samtools and bcftools.",
    "evidence": "cve:CVE-2026-116742",
    "products": [
      {
        "name": {
          "value": "htslib",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-116742",
      "aliases": [
        "CVE-2026-116742"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV4_0": {
            "version": "4.0",
            "baseScore": 4.8,
            "attackVector": "LOCAL",
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N",
            "userInteraction": "PASSIVE",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "privilegesRequired": "NONE",
            "subIntegrityImpact": "NONE",
            "vulnIntegrityImpact": "LOW",
            "subAvailabilityImpact": "NONE",
            "vulnAvailabilityImpact": "LOW",
            "subConfidentialityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE"
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        },
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            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L",
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            "userInteraction": "REQUIRED",
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            "availabilityImpact": "LOW",
            "privilegesRequired": "NONE",
            "confidentialityImpact": "NONE"
          }
        }
      ],
      "affected": [
        {
          "repo": "https://github.com/samtools/htslib",
          "vendor": "samtools",
          "product": "htslib",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "versionType": "custom",
              "lessThanOrEqual": "1.24"
            }
          ],
          "packageURL": "pkg:github/samtools/htslib",
          "defaultStatus": "unaffected"
        }
      ],
      "modified": "2026-10-27T14:16:48.820Z",
      "provider": "cve",
      "references": [
        "https://github.com/samtools/htslib/pull/2057",
        "https://github.com/samtools/htslib/commit/18dddf02bb2c0053b32acec427723555a24b2873",
        "https://github.com/samtools/htslib",
        "https://github.com/samtools/htslib/blob/1.24/bgzf.c#L2504",
        "https://hackmd.io/@haindpwn/htslib-bgzf-gzi-int-truncation-oob",
        "https://github.com/samtools/htslib/issues/2113",
        "https://www.vulncheck.com/advisories/htslib-through-1.24-heap-out-of-bounds-write-via-truncated-gzi-index-count"
      ],
      "provider_metadata": {
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            "title": "CISA ADP Vulnrichment",
            "metrics": [
              {
                "other": {
                  "type": "ssvc",
                  "content": {
                    "id": "CVE-2026-116742",
                    "role": "CISA Coordinator",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "version": "2.0.3",
                    "timestamp": "2026-10-27T13:42:04.833817Z"
                  }
                }
              }
            ],
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          "dateUpdated": "2026-10-26T21:52:41.511Z"
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    "related_cves": [
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        "value": "CVE-2026-116742",
        "evidence": "/cveMetadata/cveId"
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    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 392652,
  "published_at": "2026-10-26T21:52:41.511+00:00"
}