9.3

CVE-2021-4477: belden hirschmann hilcos openbat Improper Access Control

CVSS: 9.3v4.0CriticalAwaiting analysis
Published 03-04-2026Last modified 06-04-2026
Open JSON

Vulnerability summary

CVE-2021-4477 is a critical (CVSS 9.3) Improper Access Control vulnerability in belden hirschmann hilcos openbat. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 23.4% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.3/10
010
Critical · v4.0 (CVE.org)
EPSS score
0.32%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 03-04-2026
    PublishedVulnerability first disclosed.
  2. 06-04-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.32%

Chance of exploitation in the next 30 days

Percentile

23%

Versus all other CVEs

30-day change

0.00 pp

From 0.32% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.32%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Belden1 product
  • hirschmann hilcos openbat3.80-REL | 8.90-REL | 9.00-REL | 9.00-RU1 | 9.10-REL | 9.12-REL | 9.12-RU1 | 9.12-RU2 | 9.12-RU3 | 9.12-RU4 | 9.12-RU5 | 9.12-RU6 | 9.12-RU7 | 9.12-RU8 | 9.12-RU9 | 9.13-REL | 9.13-RU1 | 10.12-REL | 10.12-RU1

1 vendor · 1 product

References

2 links