gethostbyaddr and gethostbyaddr_r may incorrectly handle DNS response

{
  "id": "e8683e57650394508a01c6137f434a938bbf8ba6898186ceae3b1971ade7d6a6",
  "url": "https://osv.dev/vulnerability/CVE-2026-4437",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "gethostbyaddr and gethostbyaddr_r may incorrectly handle DNS response",
    "summary": "Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C Library version 2.34 to version 2.43 could, with a crafted response from the configured DNS server, result in a violation of the DNS specification that causes the application to treat a non-answer section of the DNS response as a valid answer.",
    "evidence": "osv:CVE-2026-4437",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-4437",
      "aliases": [
        "CVE-2026-4437"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://sourceware.org/git/glibc.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "ae37d06c7d127817ba43850f0f898b793d42aea7"
                },
                {
                  "last_affected": "f762ccf84f122d1354f103a151cba8bde797d521"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:gnu:glibc:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.34"
                      },
                      {
                        "last_affected": "2.43"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "glibc-2.43",
            "glibc-2.42",
            "glibc-2.42.9000",
            "glibc-2.41.9000",
            "glibc-2.41",
            "glibc-2.40",
            "glibc-2.40.9000",
            "glibc-2.39.9000",
            "glibc-2.39",
            "glibc-2.38",
            "glibc-2.38.9000",
            "glibc-2.37",
            "glibc-2.37.9000",
            "glibc-2.36",
            "glibc-2.36.9000",
            "glibc-2.35",
            "glibc-2.35.9000",
            "glibc-2.34",
            "glibc-2.34.9000"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-4437.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.494063143Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4437.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-4437",
        "https://sourceware.org/bugzilla/show_bug.cgi?id=34014"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-125"
        ],
        "cna_assigner": "glibc",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "2.34"
                  },
                  {
                    "last_affected": "2.43"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4437.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-4437",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504920,
  "published_at": "2026-03-20T19:59:00.427+00:00"
}