{
  "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-2021-4477",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2021-4477",
    "idYear": 2021,
    "status": "PUBLISHED",
    "publishedAt": "2026-04-03T22:37:45.879Z",
    "updatedAt": "2026-04-06T13:17:07.744Z",
    "importedAt": "2026-10-24T01:56:36.661Z",
    "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": "Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass",
      "summary": "Hirschmann HiLCOS OpenBAT and BAT450 products contain a firewall bypass vulnerability in IPv6 IPsec deployments that allows traffic from VPN connections to bypass configured firewall rules. Attackers can exploit this vulnerability by establishing IPv6 IPsec connections (IKEv1 or IKEv2) while simultaneously using an IPv6 Internet connection to circumvent firewall policy enforcement.",
      "affected": [
        {
          "vendor": "Belden",
          "product": "Hirschmann HiLCOS OpenBAT",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "3.80-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "8.90-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.00-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.00-RU1",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.10-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU1",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU2",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU3",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU4",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU5",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU6",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU7",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU8",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.12-RU9",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.13-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "9.13-RU1",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "10.12-REL",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "10.12-RU1",
              "status": "affected",
              "versionType": "custom"
            },
            {
              "version": "10.12-RU2",
              "status": "unaffected",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  }
}