MEDIUM
A flaw was found in the way KVM hypervisor handled x2APIC Machine Specific Rregister (MSR) access with nested(=1) virtualization enabled. In that, L1 guest could access L0's APIC register values via L2 guest, when 'virtualize x2APIC mode' is enabled. A guest could use this flaw to potentially crash the host kernel resulting in DoS issue. Kernel versions from 4.16 and newer are vulnerable to this issue.
http://www.securityfocus.com/bid/107850
https://access.redhat.com/errata/RHSA-2019:2703
https://access.redhat.com/errata/RHSA-2019:2741
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3887
https://usn.ubuntu.com/3979-1/
Source: MITRE
Published: 2019-04-09
Updated: 2019-05-21
Type: CWE-20
Base Score: 4.7
Vector: AV:L/AC:M/Au:N/C:N/I:N/A:C
Impact Score: 6.9
Exploitability Score: 3.4
Severity: MEDIUM
Base Score: 5.6
Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H
Impact Score: 4
Exploitability Score: 1.1
Severity: MEDIUM