CVE-2021-4477
Firewall bypass via IPv6 IPsec on HiLCOS OpenBAT/BAT450
Is CVE-2021-4477 being exploited?
Not confirmed. CVE-2021-4477 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.32% probability of exploitation in the next 30 days.
How severe is CVE-2021-4477?
CVE-2021-4477 is rated Critical with a CVSS score of 9.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-4477?
Not known from our data. No patch reference has been recorded for CVE-2021-4477, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2021-4477 affect?
CVE-2021-4477 affects Hirschmann HiLCOS OpenBAT, Hirschmann HiLCOS BAT450. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2021-4477?
Patch when available; restrict IPv6 IPsec/VPN access; segment affected devices
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass firewall policy via IPv6 IPsec VPN; attackers can reach protected internal networks.
Immediate action required
- affected3.80-REL
- affected8.90-REL
- affected9.00-REL
- affected9.00-RU1
- affected9.10-REL
- affected9.12-REL
- affected9.12-RU1
- affected9.12-RU2
- affected9.12-RU3
- affected9.12-RU4
- affected9.12-RU5
- affected9.12-RU6
- affected9.12-RU7
- affected9.12-RU8
- affected9.12-RU9
- affected9.13-REL
- affected9.13-RU1
- affected10.12-REL
- affected10.12-RU1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.