{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2021-27393",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2021-27393",
    "idYear": 2021,
    "status": "PUBLISHED",
    "publishedAt": "2021-04-22T20:42:21.000Z",
    "updatedAt": "2024-08-03T20:48:16.739Z",
    "importedAt": "2026-10-24T01:56:26.894Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": null,
      "summary": "A vulnerability has been identified in Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2013.08), Nucleus Source Code (Versions including affected DNS modules). The DNS client does not properly randomize UDP port numbers of DNS requests. That could allow an attacker to poison the DNS cache or spoof DNS resolving.",
      "affected": [
        {
          "vendor": "Siemens",
          "product": "Nucleus NET",
          "versions": [
            {
              "version": "All versions",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "Nucleus ReadyStart V3",
          "versions": [
            {
              "version": "All versions < V2013.08",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "Nucleus Source Code",
          "versions": [
            {
              "version": "Versions including affected DNS modules",
              "status": "affected"
            }
          ]
        }
      ]
    }
  }
}