Buffer overflow
Exploit passing in more data than software expects
A buffer overflow is a vulnerability, or means of exploiting a vulnerability, in a piece of software designed to have data passed into it. In vulnerable software, the area set up to hold this data (the buffer) is inadequately defined and controlled. Thus, by passing the right amount of data in, an attacker can overflow the buffer and place data of their choice - such as code to disable defences or download further malicious code - into an area where it will be executed by the target system.
Buffer overflows are one of the most common forms of security vulnerability.