CVE-2021-4477

Name: CVE-2021-4477
Creator: NVD / NIST
Published: 2026-04-03T23:17:01.043+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.3/10EPSS 0.32%

Last modified Jun 17, 2026

This CVE is reserved or awaiting analysis. Details will appear once published by NVD.

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.

Metrics

CVSS 3.1

9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS 4.0

9.3/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.32%

23.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-284

References

Timeline

Published: Apr 3, 2026
Last Modified: Jun 17, 2026
Status: Awaiting Analysis

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Source: NVD / NIST