Race condition in the grant table code in Xen 4.6.x through 4.9.x allows local guest OS administrators to cause a denial of service (free list corruption and host crash) or gain privileges on the host via vectors involving maptrack free list handling.
https://support.citrix.com/article/CTX225941
https://security.gentoo.org/glsa/201801-14
https://bugzilla.redhat.com/show_bug.cgi?id=1477651
http://xenbits.xen.org/xsa/advisory-228.html
http://www.securitytracker.com/id/1039175
http://www.securityfocus.com/bid/100346