Xen 3.1.1 allows virtual guest system users to cause a denial of service (hypervisor crash) by using a debug register (DR7) to set certain breakpoints.
The IATA (ata) driver in FreeBSD 6.0 and 8.0, when read access to /dev is available, allows local users to cause a denial of service (kernel panic) via a certain IOCTL request with a large count, which triggers a malloc call with a large value.