The evtchn_fifo_set_pending function in Xen 4.4.x allows local guest users to cause a denial of service (host crash) via vectors involving an uninitialized FIFO-based event channel control block when (1) binding or (2) moving an event to a different VCPU.
https://exchange.xforce.ibmcloud.com/vulnerabilities/95837
http://xenbits.xen.org/xsa/advisory-107.html