The asynchronous I/O facility in 4.4 BSD kernel does not check user credentials when setting the recipient of I/O notification, which allows local users to cause a denial of service by using certain ioctl and fcntl calls to cause the signal to be sent to an arbitrary process ID.
Denial of service in RPC portmapper allows attackers to register or unregister RPC services or spoof RPC services using a spoofed source IP address such as 127.0.0.1.