Parallels allows local users to cause a denial of service (virtual machine abort) via (1) certain INT instructions, as demonstrated by INT 0xAA; (2) an IRET instruction when an invalid address is at the top of the stack; (3) a malformed MOVNTI instruction, as demonstrated by using a register as a destination; or a write operation to (4) SEGR6 or (5) SEGR7.