CVE-2021-3656

HIGH
8.8
CVSS Score
Published: March 4, 2022 at 06:41 PM UTC
Updated: June 17, 2026 at 04:05 AM UTC
26 products affected across 3 vendorsLinux KernelFedoraEnterprise Linux

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Severity
HIGH8.8
Exploit prediction
EPSS 0.7%

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 "virt_ext" field, this issue could allow a malicious L1 to disable both VMLOAD/VMSAVE intercepts and VLS (Virtual VMLOAD/VMSAVE) 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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

4.13 ≤ v < 4.14.2454.15 ≤ v < 4.19.2054.20 ≤ v < 5.4.1425.11 ≤ v < 5.13.125.5 ≤ v < 5.10.605.145.14 rc15.14 rc25.14 rc35.14 rc45.14 rc55.14 rc6
Affected range stops below 4.14.245, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.19.205, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.10.60, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.13.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.4.142, so it looks safe — our inference, not a vendor statement
redhat-enterprise-linux (environment)
All versions
redhat-enterprise-linux (environment) · redhat-enterprise-linux-eus (environment) · redhat-enterprise-linux-for-power-little-endian (environment) · redhat-enterprise-linux-for-power-little-endian-eus (environment)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
LOCAL
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-862

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