CVE-2021-3653

Name: CVE-2021-3653
Creator: NVD / NIST
Published: 2021-09-29T20:15:08.617+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 0.41%

Last modified Jun 17, 2026

CVE-2021-3653 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. A flaw was found in the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). EPSS estimates a 0.41% chance of exploitation in the next 30 days.

Description

A flaw was found in the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). Due to improper validation of the "int_ctl" field, this issue could allow a malicious L1 to enable AVIC support (Advanced Virtual Interrupt Controller) for the L2 guest. As a result, the L2 guest would be allowed to read/write physical pages of the host, resulting in a crash of the entire system, leak of sensitive data or potential guest-to-host escape. This flaw affects Linux kernel versions prior to 5.14-rc7.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

0.41%

33.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Linux	Linux Kernel	>= 2.6.30, < 4.4.282	—
Linux	Linux Kernel	>= 4.5, < 4.9.281	—
Linux	Linux Kernel	>= 4.10, < 4.14.245	—
Linux	Linux Kernel	>= 4.15, < 4.19.205	—
Linux	Linux Kernel	>= 4.20, < 5.4.142	—
Linux	Linux Kernel	>= 5.5, < 5.10.60	—
Linux	Linux Kernel	>= 5.11, < 5.13.12	—
Linux	Linux Kernel	5.14	Rc1
Redhat	Enterprise Linux	7.0	—
Debian	Debian Linux	9.0	—

References

http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlExploit, Third Party Advisory, VDB Entry
https://bugzilla.redhat.com/show_bug.cgi?id=1983686Issue Tracking, Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/10/msg00010.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/12/msg00012.htmlMailing List, Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/08/16/1Mailing List, Patch, Third Party Advisory
http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlExploit, Third Party Advisory, VDB Entry
https://bugzilla.redhat.com/show_bug.cgi?id=1983686Issue Tracking, Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/10/msg00010.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/12/msg00012.htmlMailing List, Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/08/16/1Mailing List, Patch, Third Party Advisory

Timeline

Published: Sep 29, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-3653?

How severe is CVE-2021-3653?

CVE-2021-3653 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.41% probability of exploitation in the next 30 days.

How do I fix CVE-2021-3653?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-3653?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST