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Critical · 9.1 CVE-2021-4477 EUVD-2021-34774

Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass

Published Apr 3, 2026 · Updated Apr 6, 2026 · Assigned by VulnCheck

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.

Affected products

VendorProductAffectedFixed
Belden Hirschmann HiLCOS OpenBAT 3.80-REL, 8.90-REL, 9.00-REL, 9.00-RU1, 9.10-REL, 9.12-REL, 9.12-RU1, 9.12-RU2, 9.12-RU3, 9.12-RU4, 9.12-RU5, 9.12-RU6, 9.12-RU7, 9.12-RU8, 9.12-RU9, 9.13-REL, 9.13-RU1, 10.12-REL, 10.12-RU1 10.12-RU2

References