AUGUST 4, 2026
Live Feed
Back to database
Case File

CVE-2021-4477

CRITICAL · CVSS 9.1 EPSS 0.32% Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2026-04-03 · Last synced 2026-08-04

CyberRota Analysis

This is a critical severity vulnerability with a CVSS score of 9.1. Public exploit code or proof-of-concept references have been detected in its references.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2021-4477
Severity
CRITICAL
CVSS
9.1
EPSS
0.32%

Original 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.