When you allocate an array from memory using malloc, calloc or realloc, you should ensure that you allocate enough memory to contain an instance of the required pointer type. Calls that are assigned to a non-void pointer variable, but do not allocate enough memory will cause a buffer overflow when a field accessed on the pointer points to memory that is beyond the allocated array. Buffer overflows can lead to anything from a segmentation fault to a security vulnerability.

The highlighted call allocates memory that is too small to contain an instance of the type of the pointer, which can cause a memory overrun. Use the sizeof operator to ensure that the function call allocates enough memory for that type.

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.