CVE-2021-4477 Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass
Attackers can bypass firewall rules on Hirschmann HiLCOS devices by exploiting IPv6 IPsec configurations, allowing unauthorized traffic access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-4477?
CVE-2021-4477 is a critical vulnerability in Belden Hirschmann HiLCOS OpenBAT, published on 3 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-284
Which versions are affected by CVE-2021-4477?
How do I fix CVE-2021-4477?
No fix has been published for CVE-2021-4477 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-4477 being exploited?
There is no known exploitation of CVE-2021-4477 in the wild and no public exploit code.
Sources
Also known as GHSA-pp73-vg9m-6fvw.