An issue was discovered in Xen through 4.10.x allowing x86 HVM guest OS users to cause a denial of service (host OS infinite loop) in situations where a QEMU device model attempts to make invalid transitions between states of a request.
https://xenbits.xen.org/xsa/advisory-262.html
https://www.debian.org/security/2018/dsa-4201
https://security.gentoo.org/glsa/201810-06
https://lists.debian.org/debian-lts-announce/2018/10/msg00021.html
https://lists.debian.org/debian-lts-announce/2018/05/msg00015.html