CVE-2021-4477
A critical flaw in Hirschmann HiLCOS OpenBAT and BAT450 lets attackers bypass firewall rules by using IPv6 IPsec VPN connections. The vulnerability allows traffic that should be blocked to reach the network. It can be exploited remotely without authentication.
No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.
Who is affected
Hirschmann HiLCOS OpenBAT and BAT450 products.
Real-world impact
An attacker could send traffic through the VPN that bypasses firewall policies, potentially accessing internal resources or exfiltrating data.
Why this severity
The CVSS score of 9.3 reflects a network‑based attack that requires no authentication, with high confidentiality and integrity impact, and no user interaction.
What to do about it
No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.
No fix documented in sources
Timeline
- Apr 3, 2026 · Apr 3, 2026PublishedDisclosed and added to the National Vulnerability Database.
- Jul 24, 2026 · 11d agoAdvisory updatedThe NVD record was last revised.