Freeing memory multiple times has similar consequences to accessing memory after it is freed. The underlying data structures that manage the heap can become corrupted in a way that could introduce security vulnerabilities into a program. These types of issues are referred to as double-free vulnerabilities. In practice, double-free vulnerabilities can be exploited to execute arbitrary code. For instance, VU#62332VU#623332, which describes a double free vulnerability in the MIT Kerberos 5 function krb5_recvauth(). To eliminate double-free vulnerabilities, it is necessary to guarantee that dynamic memory is freed only once. Programmers should be wary when freeing memory in a loop or conditional statement, if coded incorrectly, these constructs can lead to double-free vulnerabilities.
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