This rule finds accesses through a pointer of a memory location that has already been freed (i.e. through a dangling pointer). Such memory blocks have already been released to the dynamic memory manager, and modifying them can lead to anything from a segfault to memory corruption that would cause subsequent calls to the dynamic memory manger to behave erratically, to a possible security vulnerability.

Ensure that all execution paths that access memory through a pointer never access that pointer after it is freed.

I. Gerg. An Overview and Example of the Buffer-Overflow Exploit. IANewsletter vol 7 no 4. 2005.

M. Donaldson. Inside the Buffer Overflow Attack: Mechanism, Method & Prevention. SANS Institute InfoSec Reading Room. 2002.