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CVE-2021-3748

26
FAUCET Score

CVE-2021-3748 is a use-after-free vulnerability in the virtio-net device of QEMU, affecting products like Canonical, Debian, FedoraProject, QEMU, and Red Hat. This high-severity flaw (CVSS 7.5) allows a malicious guest to trigger a denial of service or potentially execute code on the host with QEMU process privileges, requiring high privileges and high attack complexity. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.10.0, < 6.2.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
18.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
20.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
0.8
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.52%
Probability of exploitation in next 30 days
EPSS Percentile
41.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0052 is in the 88th percentile among its peer group of 160 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.2 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (17)

github_advisorypatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 ARMFixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: 18757-16823Fixed in: 6.2.0-2
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 x64Fixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: cbl2 qemu 6.2.0-2 on CBL Mariner 2.0Fixed in: 6.2.0-2
microsoftpatch availablevia msrc
Product: cm1 qemu-kvm 4.2.0-39 on CBL Mariner 1.0Fixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: 18887-16820Fixed in: 4.2.0-39
redhatpatch availablevia redhat_api
Product: Advanced Virtualization for RHEL 8.4.0.ZFixed in: virt-devel:av-8040020211022000504.522a0ee4
View patch
redhatpatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Advanced Virtualization for RHEL 8.2.1Fixed in: virt:8.2-8020120211120005046.863bb0db
View patch
redhatpatch availablevia redhat_api
Product: Advanced Virtualization for RHEL 8.2.1Fixed in: virt-devel:8.2-8020120211120005046.863bb0db
View patch
redhatpatch availablevia redhat_api
Product: Advanced Virtualization for RHEL 8.4.0.ZFixed in: virt:av-8040020211022000504.522a0ee4
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
ubuntupatch availablevia nvd_reference
View patch
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 8 Advanced VirtualizationFixed in: virt:av/qemu-kvm
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 8 Advanced VirtualizationFixed in: virt:8.2/qemu-kvm

Vendor Advisories (3)

microsoft2023-Mar/CVE-2021-3748

CVE-2021-3748

Mar 14, 2023
microsoft2022-Mar/CVE-2021-3748Important

A use-after-free vulnerability was found in the virtio-net device of QEMU. It could occur when the descriptor's address belongs to the non direct access region due to num_buffers being set after the virtqueue elem has been unmapped. A malicious guest could use this flaw to crash QEMU resulting in a denial of service condition or potentially execute code on the host with the privileges of the QEMU process.

Mar 8, 2022
redhatCVE-2021-3748Moderate

QEMU: virtio-net: heap use-after-free in virtio_net_receive_rcu

Aug 27, 2021

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
github.com / qemu/qemu/commit/bedd7e93d01961fcb16a97ae45d93acf357e11f6
PatchThird Party Advisory
lists.debian.org / debian-lts-announce/2022/04/msg00002.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2022/09/msg00008.html
Mailing ListThird Party Advisory
lists.nongnu.org / archive/html/qemu-devel/2021-09/msg00388.html
Mailing ListPatchThird Party Advisory
security.gentoo.org / glsa/202208-27
Third Party Advisory
security.netapp.com / advisory/ntap-20220425-0004
Third Party Advisory
ubuntu.com / security/CVE-2021-3748
PatchThird Party Advisory