Buffer Overflow Causes. ©2002, Jedidiah R. Crandall, Susan L. Gerhart, Jan G. Hogle.  http://sfsecurity.pr.erau.edu
Formatting and logical errors – Consequences.
Even if the attacker has very little control of the data that overwrites a return pointer, they can always crash the program by sending the program control to random places in memory. 
Crashing the program is a security risk for many reasons, including denial-of-service attacks and core dumps of security-sensitive data.
It’s never safe to assume that a clever attacker can’t find a way to give input that causes the output he wants.