A flaw was found in the way Linux kernel KVM hypervisor before 4.18 emulated instructions such as sgdt/sidt/fxsave/fxrstor. It did not check current privilege(CPL) level while emulating unprivileged instructions. An unprivileged guest user/process could use this flaw to potentially escalate privileges inside guest.
http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00043.html
https://access.redhat.com/errata/RHSA-2019:2029
https://access.redhat.com/errata/RHSA-2019:2043
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10853
https://lists.debian.org/debian-lts-announce/2018/07/msg00015.html
https://lists.debian.org/debian-lts-announce/2018/07/msg00016.html
https://lists.debian.org/debian-lts-announce/2018/07/msg00020.html
https://usn.ubuntu.com/3777-1/
Source: MITRE
Published: 2018-09-11
Updated: 2019-10-03
Type: CWE-269
Base Score: 4.6
Vector: AV:L/AC:L/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 3.9
Severity: MEDIUM
Base Score: 7.8
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 1.8
Severity: HIGH