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CVE-2021-4145

23
FAUCET Score

CVE-2021-4145 is a NULL pointer dereference vulnerability affecting QEMU versions prior to 6.2.0, as well as Red Hat Enterprise Linux and QEMU products. An unprivileged guest user can exploit this flaw to crash the host's QEMU process by triggering a specific condition during data mirroring. This vulnerability has a CVSS score of 6.5 (Medium), indicating a local attack vector with low complexity, resulting in high availability impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
6.1.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:6.1.0:-:*:*:*:*:*:*
6.1.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:6.1.0:rc0:*:*:*:*:*:*
6.1.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:6.1.0:rc1:*:*:*:*:*:*
6.1.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:6.1.0:rc2:*:*:*:*:*:*
6.1.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:6.1.0:rc3:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.0
Impact Score
4.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.39%
Probability of exploitation in next 30 days
EPSS Percentile
31.6%
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 87th percentile among its peer group of 15,940 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 (5)

microsoftpatch availablevia msrc
Product: 18757-16823Fixed in: 6.2.0-2
microsoftpatch availablevia msrc
Product: cbl2 qemu 6.2.0-2 on CBL Mariner 2.0Fixed in: 6.2.0-2
redhatpatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: virt-devel:rhel-8060020220408104655.d63f516d
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: virt:rhel-8060020220408104655.d63f516d
View patch

Vendor Advisories (3)

microsoft2023-Mar/CVE-2021-4145

CVE-2021-4145

Mar 14, 2023
microsoft2022-Jan/CVE-2021-4145Moderate

A NULL pointer dereference issue was found in the block mirror layer of QEMU in versions prior to 6.2.0. The `self` pointer is dereferenced in mirror_wait_on_conflicts() without ensuring that it's not NULL. A malicious unprivileged user within the guest could use this flaw to crash the QEMU process on the host when writing data reaches the threshold of mirroring node.

Jan 11, 2022
redhatCVE-2021-4145Low

QEMU: NULL pointer dereference in mirror_wait_on_conflicts() in block/mirror.c

Dec 10, 2021

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
gitlab.com / qemu-project/qemu/-/commit/66fed30c9cd11854fc878a4eceb507e915d7c9cd
PatchThird Party Advisory
security.gentoo.org / glsa/202208-27
Third Party Advisory
security.netapp.com / advisory/ntap-20220311-0004
Third Party Advisory