One of the most effective techniques to identify buffer-overflow vulnerabilities is fuzz testing. Fuzzing is the practice of testing the results associated with various input by passing crafted or random data to a function. In the right circumstances, it is possible that input data can escape its designated buffer and flow into adjacent registers or segments of memory. This process will disrupt the execution flow and result in application or system crashes. In certain circumstances, buffer-overflow vulnerabilities can also be leveraged to execute unauthorized code. In this particular recipe, we will discuss how to test for buffer-overflow vulnerabilities by developing custom fuzzing tools.