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CVE-2021-3653

8.8 · HIGH

A flaw was found in the KVM's AMD code for supporting SVM nested virtualization.

Published Sep 29, 2021CWE-862EPSS 0.45%

Overview

CVE-2021-3653 is a high-severity vulnerability. It was published on September 29, 2021 and has a CVSS 3.1 base score of 8.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refpacketstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlRefbugzilla.redhat.com/show_bug.cgi?id=1983686Reflists.debian.org/debian-lts-announce/2021/10/msg00010.htmlReflists.debian.org/debian-lts-announce/2021/12/msg00012.htmlRefwww.openwall.com/lists/oss-security/2021/08/16/1Refpacketstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlRefbugzilla.redhat.com/show_bug.cgi?id=1983686Reflists.debian.org/debian-lts-announce/2021/10/msg00010.htmlReflists.debian.org/debian-lts-announce/2021/12/msg00012.htmlRefwww.openwall.com/lists/oss-security/2021/08/16/1

How CyberStrike helps

Frequently asked questions

What is CVE-2021-3653?

CVE-2021-3653 is a high-severity vulnerability. It was published on September 29, 2021 and has a CVSS 3.1 base score of 8.8 (HIGH).

How severe is CVE-2021-3653?

This vulnerability has a CVSS 3.1 base score of 8.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-3653?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-3653?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-3653 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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