CVE•Published 2026-04-03•Modified 2026-07-24•1 article on news•4 live references•NVD data
CVE-2021-4477
Vulnerability data via NVD (ingested)
CVSS v3.1
9.1
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS percentile
24
Exploit Prediction Scoring System · top 76% of all CVEs
Weaknesses (CWE)
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.
Timeline
Published 2026-04-03
Modified 2026-07-24
External references
Search for exposed instances
Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).
More intel sources (5)
Shodan report
vuln:CVE-2021-4477Country / ASN / product breakdown for the vuln query.
Censys
vulnerabilities.cve_id: CVE-2021-4477Censys host search filtered to this CVE id.
grep.app
CVE-2021-4477Public source-code mentions — fast PoC discovery.
GitHub code
CVE-2021-4477GitHub code search for direct mentions.
Google dork
"CVE-2021-4477" exploit -site:nvd.nist.govWrite-ups and news, NVD excluded.
Known PoCs on GitHub
No public proof-of-concept repositories found for CVE-2021-4477 on GitHub.