QEMU (aka Quick Emulator), when built with the IDE disk and CD/DVD-ROM Emulator support, allows local guest OS privileged users to cause a denial of service (NULL pointer dereference and QEMU process crash) by flushing an empty CDROM device drive.
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg01850.html
http://www.securityfocus.com/bid/100451