TI-2021-03331 Aliases CVE-2021-4477 GHSA-pp73-vg9m-6fvw

Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass

MEDIUM 48CWE-284Published 2026-04-03 · Updated 2026-04-06

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Security bypass
Confidentiality · integrity · availability: High · High · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-284.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00331 26th percentileScored 2026-11-07

Fix Fixed Hirschmann HiLCOS OpenBAT (Belden): 10.12-RU2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
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	Patch available	CNA

Hirschmann HiLCOS OpenBAT VendorBelden Affected 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 Fixed in 10.12-RU2 Patch available CNA

Remediation

Fix · CNA Hirschmann HiLCOS OpenBAT (Belden) Fixed in 10.12-RU2

Timeline

2026-10-02 Threatist record created from CVE-2021-4477
2026-10-03 Alias added: GHSA-pp73-vg9m-6fvw

References

Advisory 1

https://assets.belden.com/m/5fd1a50fa50cb252/original/Belden-Security-Bulletin-BSECV-1v0-2019-09.pdf

TI-2019-09143 Wind River VxWorks has a Buffer Overflow in the TCP component (issue 1 of 4). CVSS 3.1CRITICAL 9.8
TI-2019-09145 Wind River VxWorks 6.6 through 6.9 has a Buffer Overflow in the DHCP client component. CVSS 3.1HIGH 8.8
TI-2022-19123 The web server of Hirschmann BAT-C2 before 09.13.01.00R04 allows authenticated command… CVSS 3.1HIGH 8.8
TI-2019-09144 Wind River VxWorks 6.9 and vx7 has a Buffer Overflow in the IPv4 component. CVSS 3.1CRITICAL 9.8
TI-2019-09148 Wind River VxWorks 6.9 and vx7 has a Buffer Overflow in the TCP component (issue 2 of 4). CVSS 3.1CRITICAL 9.8
TI-2025-43113 A stored cross-site scripting (XSS) vulnerability exists in the web management interface… CVSS 3.1MEDIUM 6.1

See all 49 →

Sources

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