CVE-2021-4477

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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."}, {"lang": "es", "value": "Los productos Hirschmann HiLCOS OpenBAT y BAT450 contienen una vulnerabilidad de omisi\u00f3n de cortafuegos en implementaciones IPv6 IPsec que permite que el tr\u00e1fico de las conexiones VPN omita las reglas de cortafuegos configuradas. Los atacantes pueden explotar esta vulnerabilidad al establecer conexiones IPv6 IPsec (IKEv1 o IKEv2) mientras utilizan simult\u00e1neamente una conexi\u00f3n a Internet IPv6 para eludir la aplicaci\u00f3n de la pol\u00edtica del cortafuegos."}], "id": "CVE-2021-4477", "lastModified": "2026-07-24T22:10:00.140", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.2, "source": "disclosure@vulncheck.com", "type": "Secondary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 9.3, "baseSeverity": "CRITICAL", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "disclosure@vulncheck.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-4477", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-04-06T13:16:56.315497Z", "version": "2.0.3"}}]}, "published": "2026-04-03T23:17:01.043", "references": [{"source": "disclosure@vulncheck.com", "url": "https://assets.belden.com/m/5fd1a50fa50cb252/original/Belden-Security-Bulletin-BSECV-1v0-2019-09.pdf"}, {"source": "disclosure@vulncheck.com", "url": "https://www.vulncheck.com/advisories/hirschmann-hilcos-openbat-bat450-ipv6-ipsec-firewall-bypass"}], "sourceIdentifier": "disclosure@vulncheck.com", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-284"}], "source": "disclosure@vulncheck.com", "type": "Secondary"}]}

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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "3.80-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "8.90-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.00-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.00-RU1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.10-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU3"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU4"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU5"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU6"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU7"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU8"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.12-RU9"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.13-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "9.13-RU1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "10.12-REL"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "10.12-RU1"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "10.12-RU2"}}], "enrichment": {"confidence": 100.0, "confidence_source": "manual", "scores": [{"score": 100.0, "source": "manual"}]}, "original": {"product": "Hirschmann HiLCOS OpenBAT", "source": "cna", "vendor": "Belden"}, "product": "hirschmann_hilcos_openbat", "vendor": "belden"}], "analysis": {"en": {"generated_at": "2026-04-04T01:22:41.660654+00:00", "value": {"mitigation_remediation": ["Check Belden/Hirschmann product documentation and apply the latest firmware update that patches the IPv6 IPsec firewall bypass. If an update is not yet released, disable or remove IPv6 IPsec support on the device until a fix is available. Consider enforcing additional filtering rules to reject VPN traffic that originates from external sources. Monitor device logs for unusual IPsec negotiations or traffic that appears to bypass the firewall."], "summary": {"action": "Immediate Patch", "impact": "Bypasses firewall rules for IPv6 IPsec VPN traffic"}, "threat_synthesis": {"affected_systems": "Devices from Hirschmann under the HiLCOS OpenBAT line, including the BAT450 series. The vulnerability is present in all firmware versions of these models that still support IPv6 IPsec.", "description_and_impact": "Hirschmann HiLCOS OpenBAT and BAT450 devices have a flaw that lets attackers avoid firewall configurations when they set up IPv6 IPsec VPN connections. The CVE allows an adversary to create IKEv1 or IKEv2 sessions that carry traffic directly into the protected network, effectively bypassing any packet filtering rules. This can expose internal hosts to undetected intrusion or data exfiltration because the firewall no longer sees the packets as originating from a prohibited source.", "risk_and_exploitability": "With a CVSS score of 9.3 the issue is considered critical. Exploitation requires only the ability to negotiate an IPv6 IPsec connection, which is typically achievable with remote network access and legitimate VPN credentials. Attackers can manipulate the connection parameters, so the exploit does not need privileged local access. The vulnerability is not listed in the CISA KEV catalog, and no EPSS score is available, but the high severity indicates a strong potential for real-world attacks."}}}}, "created": "2026-04-06T21:22:04.650587+00:00", "updated": "2026-04-06T22:21:42.700663+00:00", "vendors": ["belden", "belden$PRODUCT$hirschmann_hilcos_openbat"]}