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.
rpc.mountd on Linux, Ultrix, and possibly other operating systems, allows remote attackers to determine the existence of a file on the server by attempting to mount that file, which generates different error messages depending on whether the file exists or not.