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    CVE-2021-4477

    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.

    Published:Apr 3, 2026
    Last Modified:Apr 7, 2026
    EPS:Apr 3, 2026
    EPSS Score:0.00006
    CVSS Score:9.1

    Affected Products

    Vendor
    Belden
    Product
    Hirschmann Hilcos Openbat

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-284 Improper Access Control

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High