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CWE - 416 : Use After Free

CWE Definition
Number of vulnerabilities: 305
Description Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
Background Details
Other Notes The use of previously freed memory can have any number of adverse consequences -- ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system's reuse of the freed memory. Like double free errors and memory leaks, use after free errors have two common and sometimes overlapping causes: - Error conditions and other exceptional circumstances. - Confusion over which part of the program is responsible for freeing the memory. In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data chances to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

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