VulnSocial

CVE-2021-4477Disclosure

LOWCVSS 9.3 · CRITICAL

Signal is active with 1 mentions in latest observed window

Immediate actions

  • Track advisory updates for patch or workaround availability

Recommended action window: Monitor and triage in normal cycle

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.

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0.0/ 10 priority

Sources & remediation

Other references
Weakness type (CWE)
CWE-284

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

NONE

Momentum

STABLE

Threat summary

  • 2 mentions across 2 observed days
  • Momentum state: stable

What's happening

  • Technical details provided in 2 signals
  • Disclosure: 2 classified signals
  • Peaked 1d ago at 1 mentions (2026-04-03); latest day: 1
  • 2 total mentions across 2 days

Deep dive

Activity timeline2 mentions / 2d
00111Mentions · 2026-04-03: 1Mentions · 2026-04-06: 1Technical Details · 2026-04-03: 1Technical Details · 2026-04-06: 104-0304-06
Signal classification1 categories
Disclosure
2100.0%
Referenced assets2 URLs
Full discourse2 posts
  • CVEFind.com@CveFindCom
    Disclosure

    [CVE-2021-4477: CRITICAL] Security alert: Hirschmann HiLCOS OpenBAT & BAT450 have a firewall bypass vulnerability in IPv6 IPsec deployments. Attackers can exploit it to bypass firewall rules on VPN connections.#cve,CVE-2021-4477,#cybersecurity https://cvefind.com/CVE-2021-4477

    Post summary

    The post announces a critical firewall bypass vulnerability in Hirschmann HiLCOS OpenBAT & BAT450 IPv6 IPsec deployments, noting that attackers could exploit it, but no PoC, patch, or evidence of active exploitation is provided.

    0101056
    619 followersView on X
  • 0day Signal@0dayPublishing
    Disclosure

    🚨 CVE-2021-4477: Hirschmann HiLCOS OpenBAT BAT450 ... IPv6 IPsec tunnels completely bypass firewall rules on industrial Hirschmann switches - dual-stack deployments are sitti... https://zerodaysignal.com/vulnerability/CVE-2021-4477 #netsec #vulnerability #CVE #sysadmin #zeroday

    Post summary

    The tweet announces CVE-2021-4477, highlighting how IPv6 IPsec tunnels can bypass firewall rules on Hirschmann switches, but it offers no proof‑of‑concept, exploit code, patch information, or evidence of active exploitation.

    0001046
    204 followersView on X

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