CVE-2021-4032

Host kernel crash via LAPIC counter underflow

Published Jan 21, 2022 · Updated Aug 3, 2024

Denial of service in Linux Kernel KVM 5.15-rc1 through 5.15-rc6 allows local users with high privileges to crash the host kernel. During failed vCPU construction, kvm_free_lapic reads an uninitialized apic_base and decrements apic_hw_disabled without a matching increment. Triggering the faulty cleanup requires high-privilege local access and interrupts the virtualization host and its running guests.

CVSS severity4.4
Medium
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux Kernel KVM 5.15-rc1 through 5.15-rc6 allows local users with high privileges to crash the host kernel. During failed vCPU construction, kvm_free_lapic reads an uninitialized apic_base and decrements apic_hw_disabled without a matching increment. Triggering the faulty cleanup requires high-privilege local access and interrupts the virtualization host and its running guests.

The record

CVE
CVE-2021-4032
Published
Jan 21, 2022
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-459, T1499
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jan 21, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=kernel 5.15 rc7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=kernel 5.15 rc7

Published CVSS scores

4.9National Vulnerability DatabaseAV:L/AC:L/Au:N/C:N/I:N/A:C
5.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.4National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-459Incomplete Cleanup
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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