Vulnerability Details : CVE-2021-3656
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.
Products affected by CVE-2021-3656
- cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_desktop:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_eus:8.1:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_eus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_eus:8.4:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_workstation:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_aus:7.6:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_aus:7.7:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_aus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_aus:8.4:*:*:*:*:*:*:*
- cpe:2.3:a:redhat:openstack:13:*:*:*:*:*:*:*
- cpe:2.3:a:redhat:software_collections:-:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_scientific_computing:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian_eus:8.1:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian_eus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian_eus:8.4:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian:8.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_power_big_endian:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems_eus:8.1:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems_eus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems_eus:8.4:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems:7.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems:8.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time_for_nfv:7:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time_for_nfv:8:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time:7:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time:8:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_tus:7.6:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_tus:7.7:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_tus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_tus:8.4:*:*:*:*:*:*:*
- cpe:2.3:a:redhat:virtualization_host:4.0:*:*:*:*:*:*:*
- cpe:2.3:a:redhat:3scale_api_management:2.0:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time_for_nfv_tus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time_for_nfv_tus:8.4:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time_tus:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_for_real_time_tus:8.4:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_update_services_for_sap_solutions:8.1:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_update_services_for_sap_solutions:8.2:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_update_services_for_sap_solutions:8.4:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_update_services_for_sap_solutions:7.6:*:*:*:*:*:*:*
- cpe:2.3:o:redhat:enterprise_linux_server_update_services_for_sap_solutions:7.7:*:*:*:*:*:*:*
- Redhat » Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions » Version: 8.1cpe:2.3:o:redhat:enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions:8.1:*:*:*:*:*:*:*
- Redhat » Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions » Version: 8.2cpe:2.3:o:redhat:enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions:8.2:*:*:*:*:*:*:*
- Redhat » Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions » Version: 8.4cpe:2.3:o:redhat:enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions:8.4:*:*:*:*:*:*:*
- Redhat » Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions » Version: 7.6cpe:2.3:o:redhat:enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions:7.6:*:*:*:*:*:*:*
- cpe:2.3:a:redhat:codeready_linux_builder:-:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:-:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:rc1:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:rc2:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:rc3:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:rc4:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:rc5:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.14:rc6:*:*:*:*:*:*
- cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
- cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
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 65,713
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
0.02%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 3 %
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
-
https://www.openwall.com/lists/oss-security/2021/08/16/1
oss-security - [CVE-2021-3653, CVE-2021-3656] SVM nested virtualization issues in KVMMailing List;Third Party Advisory
-
https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc
KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656) · torvalds/linux@c7dfa40 · GitHubPatch;Third Party Advisory
-
https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc
kvm/kvm.git - kernel-based virtual machine - kvmPatch;Third Party Advisory
-
https://bugzilla.redhat.com/show_bug.cgi?id=1983988
1983988 – (CVE-2021-3656) CVE-2021-3656 kernel: SVM nested virtualization issue in KVM (VMLOAD/VMSAVE)Issue Tracking;Third Party Advisory
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