CVE-2021-4477CWE-284

Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass

Critical · published April 3, 2026

CVSS v4.0
9.3
EPSS
0%
Percentile
23.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
9.3 · CRITICAL
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
EPSS
0.00319 · 23.6th percentile
Weakness
CWE-284 · Improper Access Control
Published
2026-04-03T22:37Z
EPSS history
Timeline
  • 03 APR 22:37Z
    Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass
    cvelistv5