An issue was discovered in Xen through 4.10.x allowing x86 PV guest OS users to cause a denial of service (host OS CPU hang) via non-preemptable L3/L4 pagetable freeing.
https://xenbits.xen.org/xsa/advisory-252.html
https://www.debian.org/security/2018/dsa-4131
https://support.citrix.com/article/CTX232655
https://support.citrix.com/article/CTX232096
https://security.gentoo.org/glsa/201810-06
https://lists.debian.org/debian-lts-announce/2018/11/msg00013.html
https://lists.debian.org/debian-lts-announce/2018/03/msg00003.html