Is CVE-2021-3656 in the CISA KEV catalog?

No. CVE-2021-3656 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-3656?

CVE-2021-3656 has a CVSS v3 base score of 8.8 (HIGH).

What is the EPSS score for CVE-2021-3656?

CVE-2021-3656 has an EPSS score of 0.66% (47th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-3656?

Upgrade linux on debian 11 to 5.10.46-5 or later. Fixes are available for 114 affected products.

CVE & CISA-KEV Catalog

CVE-2021-3656

HIGH

8.8

CVSS v3

NVD

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.

CWE-862Missing Authorization

How to fix

Remediation Available

linuxDebian

Fixed in:5.10.46-5CVE-2021-3656

Fixed in:5.14.6-1CVE-2021-3656

gcpUbuntu

Fixed in:5.4.0-1009LSN-0081-1

generic-4.15Ubuntu

Fixed in:4.15.0-69LSN-0081-1

generic-4.4Ubuntu

Fixed in:4.4.0-168LSN-0081-1

Fixed in:4.4.0-211LSN-0081-1

generic-5.4Ubuntu

Fixed in:5.4.0-26LSN-0081-1

gkeUbuntu

Fixed in:5.4.0-1033LSN-0081-1

gke-4.15Ubuntu

Fixed in:4.15.0-1076LSN-0081-1

gke-5.4Ubuntu

Fixed in:5.4.0-1009LSN-0081-1

gkeopUbuntu

Fixed in:5.4.0-1009LSN-0081-1

gkeop-5.4Ubuntu

Fixed in:5.4.0-1007LSN-0081-1

linuxUbuntu

Fixed in:4.15.0-156.163USN-5073-1

Fixed in:5.4.0-84.94USN-5071-1

linux-awsUbuntu

Fixed in:4.15.0-1111.118USN-5073-1

Fixed in:5.4.0-1056.59USN-5071-1

linux-aws-5.11Ubuntu

Fixed in:5.11.0-1017.18~20.04.1USN-5070-1

linux-aws-5.4Ubuntu

Fixed in:5.4.0-1056.59~18.04.1USN-5071-1

linux-aws-hweUbuntu

Fixed in:4.15.0-1111.118~16.04.1USN-5073-1

linux-azureUbuntu

Fixed in:4.15.0-1123.136~14.04.1USN-5073-1

Fixed in:4.15.0-1123.136~16.04.1USN-5073-1

Fixed in:5.4.0-1058.60USN-5071-1

linux-azure-4.15Ubuntu

Fixed in:4.15.0-1123.136USN-5073-1

linux-azure-5.11Ubuntu

Fixed in:5.11.0-1015.16~20.04.1USN-5070-1

linux-azure-5.4Ubuntu

Fixed in:5.4.0-1058.60~18.04.1USN-5071-1

linux-azure-5.8Ubuntu

Fixed in:5.8.0-1041.44~20.04.1USN-5072-1

linux-dell300xUbuntu

Fixed in:4.15.0-1027.32USN-5073-1

linux-gcpUbuntu

Fixed in:4.15.0-1108.122~16.04.1USN-5073-2

Fixed in:5.4.0-1052.56USN-5071-1

linux-gcp-4.15Ubuntu

Fixed in:4.15.0-1108.122USN-5073-2

linux-gcp-5.4Ubuntu

Fixed in:5.4.0-1052.56~18.04.1USN-5071-1

linux-gkeUbuntu

Fixed in:5.4.0-1052.55USN-5071-1

linux-gke-5.4Ubuntu

Fixed in:5.4.0-1052.55~18.04.1USN-5071-1

linux-gkeopUbuntu

Fixed in:5.4.0-1023.24USN-5071-1

linux-gkeop-5.4Ubuntu

Fixed in:5.4.0-1023.24~18.04.1USN-5071-1

linux-hweUbuntu

Fixed in:4.15.0-156.163~16.04.1USN-5073-1

linux-hwe-5.11Ubuntu

Fixed in:5.11.0-34.36~20.04.1USN-5070-1

linux-hwe-5.4Ubuntu

Fixed in:5.4.0-84.94~18.04.1USN-5071-2

linux-image-4.15.0-1027-dell300xUbuntu

Fixed in:4.15.0-1027.32USN-5073-1

linux-image-4.15.0-1080-oracleUbuntu

Fixed in:4.15.0-1080.88~16.04.1USN-5073-1

Fixed in:4.15.0-1080.88USN-5073-1

linux-image-4.15.0-1099-kvmUbuntu

Fixed in:4.15.0-1099.101USN-5073-1

linux-image-4.15.0-1108-gcpUbuntu

Fixed in:4.15.0-1108.122~16.04.1USN-5073-2

Fixed in:4.15.0-1108.122USN-5073-2

linux-image-4.15.0-1111-awsUbuntu

Fixed in:4.15.0-1111.118~16.04.1USN-5073-1

Fixed in:4.15.0-1111.118USN-5073-1

linux-image-4.15.0-1112-snapdragonUbuntu

Fixed in:4.15.0-1112.121USN-5073-1

linux-image-4.15.0-1123-azureUbuntu

Fixed in:4.15.0-1123.136~14.04.1USN-5073-1

Fixed in:4.15.0-1123.136~16.04.1USN-5073-1

Fixed in:4.15.0-1123.136USN-5073-1

linux-image-4.15.0-156-genericUbuntu

Fixed in:4.15.0-156.163~16.04.1USN-5073-1

Fixed in:4.15.0-156.163USN-5073-1

linux-image-4.15.0-156-generic-lpaeUbuntu

Fixed in:4.15.0-156.163USN-5073-1

linux-image-4.15.0-156-lowlatencyUbuntu

Fixed in:4.15.0-156.163~16.04.1USN-5073-1

Fixed in:4.15.0-156.163USN-5073-1

linux-image-5.10.0-1045-oemUbuntu

Fixed in:5.10.0-1045.47USN-5072-1

linux-image-5.11.0-1015-azureUbuntu

Fixed in:5.11.0-1015.16~20.04.1USN-5070-1

linux-image-5.11.0-1017-awsUbuntu

Fixed in:5.11.0-1017.18~20.04.1USN-5070-1

linux-image-5.11.0-1017-oracleUbuntu

Fixed in:5.11.0-1017.18~20.04.1USN-5070-1

linux-image-5.11.0-34-genericUbuntu

Fixed in:5.11.0-34.36~20.04.1USN-5070-1

linux-image-5.11.0-34-generic-64kUbuntu

Fixed in:5.11.0-34.36~20.04.1USN-5070-1

linux-image-5.11.0-34-generic-lpaeUbuntu

Fixed in:5.11.0-34.36~20.04.1USN-5070-1

linux-image-5.11.0-34-lowlatencyUbuntu

Fixed in:5.11.0-34.36~20.04.1USN-5070-1

linux-image-5.13.0-1012-oemUbuntu

Fixed in:5.13.0-1012.16USN-5082-1

linux-image-5.4.0-1023-gkeopUbuntu

Fixed in:5.4.0-1023.24~18.04.1USN-5071-1

Fixed in:5.4.0-1023.24USN-5071-1

linux-image-5.4.0-1046-kvmUbuntu

Fixed in:5.4.0-1046.48USN-5071-1

linux-image-5.4.0-1052-gcpUbuntu

Fixed in:5.4.0-1052.56~18.04.1USN-5071-1

Fixed in:5.4.0-1052.56USN-5071-1

linux-image-5.4.0-1052-gkeUbuntu

Fixed in:5.4.0-1052.55~18.04.1USN-5071-1

Fixed in:5.4.0-1052.55USN-5071-1

linux-image-5.4.0-1054-oracleUbuntu

Fixed in:5.4.0-1054.58~18.04.1USN-5071-1

Fixed in:5.4.0-1054.58USN-5071-1

linux-image-5.4.0-1056-awsUbuntu

Fixed in:5.4.0-1056.59~18.04.1USN-5071-1

Fixed in:5.4.0-1056.59USN-5071-1

linux-image-5.4.0-1058-azureUbuntu

Fixed in:5.4.0-1058.60~18.04.1USN-5071-1

Fixed in:5.4.0-1058.60USN-5071-1

linux-image-5.4.0-84-genericUbuntu

Fixed in:5.4.0-84.94~18.04.1USN-5071-2

Fixed in:5.4.0-84.94USN-5071-1

linux-image-5.4.0-84-generic-lpaeUbuntu

Fixed in:5.4.0-84.94~18.04.1USN-5071-2

Fixed in:5.4.0-84.94USN-5071-1

linux-image-5.4.0-84-lowlatencyUbuntu

Fixed in:5.4.0-84.94~18.04.1USN-5071-2

Fixed in:5.4.0-84.94USN-5071-1

linux-image-5.8.0-1041-azureUbuntu

Fixed in:5.8.0-1041.44~20.04.1USN-5072-1

linux-image-awsUbuntu

Fixed in:5.4.0.1056.39USN-5071-1

Fixed in:5.11.0.1017.18~20.04.16USN-5070-1

linux-image-aws-hweUbuntu

Fixed in:4.15.0.1111.102USN-5073-1

linux-image-aws-lts-18.04Ubuntu

Fixed in:4.15.0.1111.114USN-5073-1

linux-image-aws-lts-20.04Ubuntu

Fixed in:5.4.0.1056.59USN-5071-1

linux-image-azureUbuntu

Fixed in:4.15.0.1123.96USN-5073-1

Fixed in:4.15.0.1123.114USN-5073-1

Fixed in:5.4.0.1058.38USN-5071-1

Fixed in:5.8.0.1041.44~20.04.13USN-5072-1

linux-image-azure-lts-18.04Ubuntu

Fixed in:4.15.0.1123.96USN-5073-1

linux-image-azure-lts-20.04Ubuntu

Fixed in:5.4.0.1058.56USN-5071-1

linux-image-dell300xUbuntu

Fixed in:4.15.0.1027.29USN-5073-1

linux-image-gcpUbuntu

Fixed in:4.15.0.1108.109USN-5073-2

Fixed in:5.4.0.1052.38USN-5071-1

linux-image-gcp-lts-18.04Ubuntu

Fixed in:4.15.0.1108.127USN-5073-2

linux-image-gcp-lts-20.04Ubuntu

Fixed in:5.4.0.1052.62USN-5071-1

linux-image-genericUbuntu

Fixed in:4.15.0.156.145USN-5073-1

Fixed in:5.4.0.84.88USN-5071-1

linux-image-generic-64k-hwe-20.04Ubuntu

Fixed in:5.11.0.34.36~20.04.13USN-5070-1

linux-image-generic-hwe-16.04Ubuntu

Fixed in:4.15.0.156.149USN-5073-1

linux-image-generic-hwe-18.04Ubuntu

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

linux-image-generic-hwe-20.04Ubuntu

Fixed in:5.11.0.34.36~20.04.13USN-5070-1

linux-image-generic-lpaeUbuntu

Fixed in:4.15.0.156.145USN-5073-1

Fixed in:5.4.0.84.88USN-5071-1

linux-image-generic-lpae-hwe-18.04Ubuntu

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

linux-image-generic-lpae-hwe-20.04Ubuntu

Fixed in:5.11.0.34.36~20.04.13USN-5070-1

linux-image-gkeUbuntu

Fixed in:4.15.0.1108.109USN-5073-2

Fixed in:5.4.0.1052.62USN-5071-1

linux-image-gke-5.4Ubuntu

Fixed in:5.4.0.1052.55~18.04.17USN-5071-1

Fixed in:5.4.0.1052.62USN-5071-1

linux-image-gkeopUbuntu

Fixed in:5.4.0.1023.26USN-5071-1

linux-image-gkeop-5.4Ubuntu

Fixed in:5.4.0.1023.24~18.04.24USN-5071-1

Fixed in:5.4.0.1023.26USN-5071-1

linux-image-kvmUbuntu

Fixed in:4.15.0.1099.95USN-5073-1

Fixed in:5.4.0.1046.45USN-5071-1

linux-image-lowlatencyUbuntu

Fixed in:4.15.0.156.145USN-5073-1

Fixed in:5.4.0.84.88USN-5071-1

linux-image-lowlatency-hwe-16.04Ubuntu

Fixed in:4.15.0.156.149USN-5073-1

linux-image-lowlatency-hwe-18.04Ubuntu

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

linux-image-lowlatency-hwe-20.04Ubuntu

Fixed in:5.11.0.34.36~20.04.13USN-5070-1

linux-image-oemUbuntu

Fixed in:4.15.0.156.149USN-5073-1

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

Fixed in:5.4.0.84.88USN-5071-1

linux-image-oem-20.04Ubuntu

Fixed in:5.10.0.1045.47USN-5072-1

linux-image-oem-20.04bUbuntu

Fixed in:5.10.0.1045.47USN-5072-1

linux-image-oem-20.04cUbuntu

Fixed in:5.13.0.1012.16USN-5082-1

linux-image-oem-osp1Ubuntu

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

Fixed in:5.4.0.84.88USN-5071-1

linux-image-oracleUbuntu

Fixed in:4.15.0.1080.68USN-5073-1

Fixed in:5.4.0.1054.58~18.04.34USN-5071-1

Fixed in:5.11.0.1017.18~20.04.10USN-5070-1

linux-image-oracle-lts-18.04Ubuntu

Fixed in:4.15.0.1080.90USN-5073-1

linux-image-oracle-lts-20.04Ubuntu

Fixed in:5.4.0.1054.54USN-5071-1

linux-image-snapdragonUbuntu

Fixed in:4.15.0.1112.115USN-5073-1

linux-image-snapdragon-hwe-18.04Ubuntu

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

linux-image-virtualUbuntu

Fixed in:4.15.0.156.145USN-5073-1

Fixed in:5.4.0.84.88USN-5071-1

linux-image-virtual-hwe-16.04Ubuntu

Fixed in:4.15.0.156.149USN-5073-1

linux-image-virtual-hwe-18.04Ubuntu

Fixed in:5.4.0.84.94~18.04.75USN-5071-2

linux-image-virtual-hwe-20.04Ubuntu

Fixed in:5.11.0.34.36~20.04.13USN-5070-1

linux-kvmUbuntu

Fixed in:4.15.0-1099.101USN-5073-1

Fixed in:5.4.0-1046.48USN-5071-1

linux-oem-5.10Ubuntu

Fixed in:5.10.0-1045.47USN-5072-1

linux-oem-5.13Ubuntu

Fixed in:5.13.0-1012.16USN-5082-1

linux-oracleUbuntu

Fixed in:4.15.0-1080.88~16.04.1USN-5073-1

Fixed in:4.15.0-1080.88USN-5073-1

Fixed in:5.4.0-1054.58USN-5071-1

linux-oracle-5.11Ubuntu

Fixed in:5.11.0-1017.18~20.04.1USN-5070-1

linux-oracle-5.4Ubuntu

Fixed in:5.4.0-1054.58~18.04.1USN-5071-1

linux-snapdragonUbuntu

Fixed in:4.15.0-1112.121USN-5073-1

lowlatency-4.15Ubuntu

Fixed in:4.15.0-69LSN-0081-1

lowlatency-4.4Ubuntu

Fixed in:4.4.0-168LSN-0081-1

Fixed in:4.4.0-211LSN-0081-1

lowlatency-5.4Ubuntu

Fixed in:5.4.0-26LSN-0081-1

oemUbuntu

Fixed in:4.15.0-1063LSN-0081-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

0.66%probability of exploitation in 30 days

47thpercentile

Moderate risk: more likely to be exploited than 47% of all known CVEs.

References

Patch2

Third-Party Advisory2

Related Vulnerabilities

Other CWE-862 (Missing Authorization) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2021-39226	Critical	9.8	100%	KEV	Fix
CVE-2022-0543	Critical	10.0	100%	KEV	Fix
CVE-2021-21978	Critical	9.8	99%	-	Fix
CVE-2023-52163	High	8.8	96%	KEV	-
CVE-2022-1329	High	8.8	93%	-	-
CVE-2023-6875	Critical	9.8	90%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.