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.
4.15.0-1041.45~14.04.14.15.0-1035.37~16.04.14.15.0-1041.454.15.0-1029.31~16.04.14.15.0-47.50~16.04.14.15.0-1010.12~16.04.14.15.0-47.504.15.0-1035.374.18.0-1011.11~18.04.14.15.0-1029.31Exploitability
AV:LAC:LPR:LUI:NScope
S:UImpact
C:HI:HA:HCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H