CVE-2021-4477

CRITICAL SEVERITY

CVSS Score & Metrics

Base Score

9.1 / 10

Vector String

                                        CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N                                    

Vulnerability 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.

Vulnerability Details

Published Date

April 03, 2026

Last Modified

April 07, 2026

CWE ID

CWE-284

Source

NVD

External References

https://assets.belden.com/m/5fd1a50fa50cb252/original/Belden-Security-Bulletin-BSECV-1v0-2019-09.pdf
https://www.vulncheck.com/advisories/hirschmann-hilcos-openbat-bat450-ipv6-ipsec-firewall-bypass

CVE-2021-4477

CVSS Score & Metrics

Vulnerability Description

Vulnerability Details

External References

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