...
In the following example, {{buff} is written to after it has been freed. These vulnerabilities can be relatively easily exploited to run arbitrary code with the permissions of the vulnerable process and are seldom this obvious. Typically, allocations and frees are far removed making it difficult to recognize and diagnose these problems.
...
Reading memory that has already been freed can lead to abnormal program termination and denial-of-service attacks.
Writing memory that has already been freed can lead to the execution of arbitrary code with the permissions of the vulnerable process.
...