An issue was discovered in the Linux kernel through 4.17.11, as used in Xen through 4.11.x. The xen_failsafe_callback entry point in arch/x86/entry/entry_64.S does not properly maintain RBX, which allows local users to cause a denial of service (uninitialized memory usage and system crash). Within Xen, 64-bit x86 PV Linux guest OS users can trigger a guest OS crash or possibly gain privileges.
http://www.securityfocus.com/bid/104924
http://www.securitytracker.com/id/1041397
https://lists.debian.org/debian-lts-announce/2018/10/msg00003.html
https://usn.ubuntu.com/3931-1/
https://usn.ubuntu.com/3931-2/
Source: MITRE
Published: 2018-07-28
Updated: 2019-10-03
Type: CWE-665
Base Score: 7.2
Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 3.9
Severity: HIGH
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