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.
Published 2022-03-04 19:15:09
Updated 2023-01-19 15:53:15
Source Red Hat, Inc.
View at NVD,   CVE.org

Threat overview for CVE-2021-3656

Top countries where our scanners detected CVE-2021-3656
Top open port discovered on systems with this issue 53
IPs affected by CVE-2021-3656 65,493
Threat actors abusing to this issue? Yes
Find out if you* are affected by CVE-2021-3656!
*Directly or indirectly through your vendors, service providers and 3rd parties. Powered by attack surface intelligence from SecurityScorecard.

Exploit prediction scoring system (EPSS) score for CVE-2021-3656

0.04%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 6 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2021-3656

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
7.2
HIGH AV:L/AC:L/Au:N/C:C/I:C/A:C
3.9
10.0
NIST
8.8
HIGH CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
2.0
6.0
NIST

CWE ids for CVE-2021-3656

  • The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
    Assigned by:
    • nvd@nist.gov (Primary)
    • secalert@redhat.com (Secondary)

References for CVE-2021-3656

Products affected by CVE-2021-3656

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