CVE-2021-3656
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.66%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 8.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 0.66% probability · 50th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-862
- Affected
- linux/linux kernel · fedoraproject/fedora · redhat/software collections · redhat/openstack · redhat/enterprise linux · redhat/enterprise linux desktop · redhat/enterprise linux eus · 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 · redhat/enterprise linux for scientific computing · redhat/enterprise linux server · redhat/enterprise linux server aus · redhat/enterprise linux server for power little endian update services for sap solutions · +6 more
- Source
- secalert@redhat.com
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1983988Issue Tracking, Third Party Advisory
- https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bcPatch, Third Party Advisory
- https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bcPatch, Third Party Advisory
- https://www.openwall.com/lists/oss-security/2021/08/16/1Mailing List, Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1983988Issue Tracking, Third Party Advisory
- https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bcPatch, Third Party Advisory
- https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bcPatch, Third Party Advisory
- https://www.openwall.com/lists/oss-security/2021/08/16/1Mailing List, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.