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.

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Fixes

Solution

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Workaround

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History

Tue, 07 Apr 2026 00:00:00 +0000

Type Values Removed Values Added
First Time appeared Belden
Belden hirschmann Hilcos Openbat
Vendors & Products Belden
Belden hirschmann Hilcos Openbat

Mon, 06 Apr 2026 14:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Fri, 03 Apr 2026 22:45:00 +0000

Type Values Removed Values Added
Description 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.
Title Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass
Weaknesses CWE-284
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

cvssV4_0

{'score': 9.3, 'vector': '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'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-04-06T13:17:07.744Z

Reserved: 2026-04-03T16:46:37.018Z

Link: CVE-2021-4477

cve-icon Vulnrichment

Updated: 2026-04-06T13:17:02.444Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-04-03T23:17:01.043

Modified: 2026-04-07T13:20:55.200

Link: CVE-2021-4477

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-04-06T22:21:42Z

Weaknesses