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CVE-2021-4477

Hirschmann HiLCOS OpenBAT BAT450 IPv6 IPsec Firewall Bypass

Published: Apr 3, 2026Updated: Apr 7, 2026 Sources: CVE List NVDCWE-284
NVD MITRE
9.1CVSSCRITICAL
EPSS Score
0.3%
Top 76.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-284

Affected Products

Hirschmann HiLCOS OpenBATBeldenNetworking Infrastructure
beldencommercialUSNetworking Infrastructureaka belden hirschmann, tofino security appliance

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

References

https://assets.belden.com/m/5fd1a50fa50cb252/original/Belden-Security-Bulletin-BSECV-1v0-2019-09.pdf
assets.belden.com
https://www.vulncheck.com/advisories/hirschmann-hilcos-openbat-bat450-ipv6-ipsec-firewall-bypass
vulncheck.com

Timeline

Published
Apr 3, 2026
Last Updated
Apr 7, 2026

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