Exim is a freely available, open source Mail Transport Agent (MTA). It is distributed and maintained by the University of Cambridge. It is available for the Unix and Linux Operating Systems.

It may be possible for local users to take advantage of a buffer overflow in exim. When exim is executed with a combination of flags, one of which is always the configuration file flag (-C), an overflow occurs. Typically, an argument of 32768 bytes must be supplied with the -C flag, and other arguments, such as the full name flag (-F), must be included with an argument of 32700 bytes.