arch/x86/kvm/mmu.c in the Linux kernel through 4.13.5, when nested virtualisation is used, does not properly traverse guest pagetable entries to resolve a guest virtual address, which allows L1 guest OS users to execute arbitrary code on the host OS or cause a denial of service (incorrect index during page walking, and host OS crash), aka an "MMU potential stack buffer overrun."
http://www.securityfocus.com/bid/101267
https://access.redhat.com/errata/RHSA-2018:0395
https://access.redhat.com/errata/RHSA-2018:0412
https://bugzilla.redhat.com/show_bug.cgi?id=1500380
Source: MITRE
Published: 2017-10-11
Updated: 2018-03-08
Type: CWE-22
Base Score: 6.9
Vector: AV:L/AC:M/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 3.4
Severity: MEDIUM
Base Score: 7.8
Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Impact Score: 6
Exploitability Score: 1.1
Severity: HIGH