libmcrypt versions prior to 2.5.5 contain a number of buffer overflow
vulnerabilities that stem from improper or lacking input validation. By
passing a longer than expected input to a number of functions (multiple
functions are affected) the user can successful make libmcrypt crash.
Another vulnerability is due to the way libmcrypt loads algorithms via
libtool. When the algorithms are loaded dynamically the each time the
algorithm is loaded a small (few kilobytes) of memory are leaked. In a
persistant enviroment (web server) this could lead to a memory exhaustion
attack that will exhaust all avaliable memory by launching repeated
requests at an application utilizing the mcrypt library.
