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Apexward Pulse
Type Vulnerability

Linux · Memory corruption

Linux Kernel Heap Out-of-Bounds Write Vulnerability

1 sourceCVE-2021-22555

At a glance

Medium
7-day window, from the last update
ActiveConfirmed in-the-wild exploitation
Evidence-weighted, not popularity
Signal

Actively exploited in the wild — prioritise confirming exposure.

Why Medium

Medium rather than High: exposure is scored at a default because we cannot see your systems or suppliers. If you run or depend on Linux Kernel, treat it as High.

Briefing

  • Do not treat uncorroborated claims as confirmed breaches.

Questions to ask IT

  • Do we run Linux Kernel, and which versions?
  • Is any of it reachable from the internet?
  • Have we checked whether it has already been used against us?
  • If it is not yet patched, what mitigation is in place, and will the fix be done by 11 Nov?

Next steps

  1. Confirm exposure, mitigation status and any service interruption risk.

Summary

  • Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space.
  • CVE-2021-22555 is listed in known-exploited catalogue (exploitation in the wild)
  • Authoritative catalogues report active exploitation of this vulnerability.

Why this matters in the UK

  • Known-exploited catalogue reports exploitation in the wild

Products and services involved

9 reports

Part of Broadcom VMWare ESX Insufficient Logging Vulnerability

All 9 reports in this story

Pulse

Last checked 4d ago · Recheck overdue since 5 Nov 2026, 23:08 UK time · 2 quiet checks collapsed

Signal
4 Nov 2026, 23:08 UK time · 4d ago

in the next 30 days first recorded at 78.7% (elevated likelihood signal, not confirmed exploitation). Suggested changed to 7d.

Elevated — confirm exposure; this is a probability signal, not confirmed exploitation.

EscalationDe-escalationCritical / liveWhat these mean
Drag to pan · Ctrl / ⌘ + scroll or pinch to zoom7 events

2 quiet checks hidden.

Sources

How we know

Statements extracted from sources. Higher confidence means stronger corroboration.

  • ConfirmedHeadline90% confidence

    Linux Kernel Heap Out-of-Bounds Write Vulnerability

  • ConfirmedSummary fact75% confidence

    Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space. Affects Linux Kernel. Known ransomware campaign use: Unknown. Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

  • ConfirmedCVE identifier95% confidence

    Event involves CVE-2021-22555

  • ConfirmedKnown-exploited catalogue98% confidence

    CVE-2021-22555 is listed in known-exploited catalogue (exploitation in the wild)