Firewall Bypass Vulnerability in Hirschmann HiLCOS OpenBAT and BAT450 Products
CVE-2021-4477

9.3CRITICAL

Key Information:

Vendor

Belden

Vendor
CVE Published:
3 April 2026

What is CVE-2021-4477?

Hirschmann HiLCOS OpenBAT and BAT450 products contain a vulnerability that enables a firewall bypass specifically within IPv6 IPsec deployments. This flaw allows attackers to establish IPv6 IPsec connections (using either IKEv1 or IKEv2) while utilizing an IPv6 Internet connection, which leads to the circumvention of configured firewall rules. As a result, malicious traffic from VPN connections can access the network without proper enforcement of firewall policies, exposing systems to potential attacks.

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Affected Version(s)

Hirschmann HiLCOS OpenBAT 3.80-REL

Hirschmann HiLCOS OpenBAT 8.90-REL

Hirschmann HiLCOS OpenBAT 9.00-REL

References

CVSS V4

Score:
9.3
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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