Vulnerability CVE-2021-3656


Published: 2022-03-04

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.

Type:

CWE-862

(Missing Authorization)

CVSS2 => (AV:L/AC:L/Au:N/C:C/I:C/A:C)

CVSS Base Score
Impact Subscore
Exploitability Subscore
7.2/10
10/10
3.9/10
Exploit range
Attack complexity
Authentication
Local
Low
No required
Confidentiality impact
Integrity impact
Availability impact
Complete
Complete
Complete
Affected software
Redhat -> Enterprise linux for scientific computing 
Redhat -> Enterprise linux server 
Redhat -> Enterprise linux server aus 
Redhat -> Openstack 
Redhat -> Enterprise linux server for power little endian update services for sap solutions 
Redhat -> Enterprise linux 
Redhat -> Enterprise linux server tus 
Redhat -> Enterprise linux desktop 
Redhat -> Enterprise linux server update services for sap solutions 
Redhat -> Enterprise linux eus 
Redhat -> Enterprise linux workstation 
Redhat -> Enterprise linux for ibm z systems 
Redhat -> Enterprise linux for ibm z systems eus 
Redhat -> Enterprise linux for power big endian 
Redhat -> Enterprise linux for power little endian 
Redhat -> Enterprise linux for power little endian eus 
Redhat -> Enterprise linux for real time 
Redhat -> Enterprise linux for real time for nfv 
Redhat -> Enterprise linux for real time for nfv tus 
Redhat -> Enterprise linux for real time tus 
Linux -> Linux kernel 
Fedoraproject -> Fedora 

 References:
https://www.openwall.com/lists/oss-security/2021/08/16/1
https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc
https://bugzilla.redhat.com/show_bug.cgi?id=1983988
https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc

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