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CVE-2021-4032

18
FAUCET Score

CVE-2021-4032 is a denial-of-service vulnerability in the Linux kernel's KVM subsystem, specifically in the kvm_free_lapic function, affecting kernel versions prior to 5.15 rc7. This flaw allows a highly privileged local attacker to crash the kernel by mishandling memory allocation errors during virtual CPU construction. With a CVSS score of 4.4 (Medium), it requires high privileges and local access to exploit, resulting in a high impact on availability. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
<= 5.14CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
5.15CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.15:-:*:*:*:*:*:*
5.15CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:*
5.15CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:*
5.15CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.4MEDIUM

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
0.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.39%
Probability of exploitation in next 30 days
EPSS Percentile
31.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0039 is in the 81st percentile among its peer group of 3,720 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

microsoftpatch availablevia msrc
Product: 18780-16820Fixed in: -
microsoftpatch availablevia msrc
Product: cm1 kernel 5.10.102.1-1 on CBL Mariner 1.0Fixed in: -
redhatpatch availablevia nvd_reference
View patch

Vendor Advisories (2)

microsoft2022-Jan/CVE-2021-4032Moderate

A vulnerability was found in the Linux kernel's KVM subsystem in arch/x86/kvm/lapic.c kvm_free_lapic when a failure allocation was detected. In this flaw the KVM subsystem may crash the kernel due to mishandling of memory errors that happens during VCPU construction which allows an attacker with special user privilege to cause a denial of service. This flaw affects kernel versions prior to 5.15 rc7.

Jan 11, 2022
redhatCVE-2021-4032Moderate

kernel: kvm: mishandling of memory error during VCPU construction can lead to DoS

Sep 8, 2021

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
git.kernel.org / pub/scm/linux/kernel/git/torvalds/linux.git/commit
ExploitPatchThird Party Advisory
lkml.org / lkml/2021/9/8/587
ExploitThird Party Advisory