Question

How integer overflow can be exploited for buffer overflow attacks?

Answer 1

A buffer overflow, or buffer overrun, is a common software coding mistake that an attacker could exploit to gain access to your system. A buffer overflow, or buffer overrun, occurs when more data is put into a fixed-length buffer than the buffer can handle. The extra information, which has to go somewhere, can overflow into adjacent memory space, corrupting or overwriting the data held in that space. This overflow usually results in a system crash, but it also creates the opportunity for an attacker to run arbitrary code or manipulate the coding errors to prompt malicious actions.

An Integer Overflow is the condition that occurs when the result of an arithmetic operation, such as multiplication or addition, exceeds the maximum size of the integer type used to store it. Attackers can use these conditions to influence the value of variables in ways that the programmer did not intend. The security impact depends on the actions taken based on those variables. An integer overflow during a buffer length calculation can result in allocating a buffer that is too small to hold the data to be copied into it.  

Cybercriminals exploit buffer overflow problems to alter the execution path of the application by overwriting parts of its memory. The malicious extra data may contain code designed to trigger specific actions — in effect sending new instructions to the attacked application that could result in unauthorized access to the system.

This is how integer overflow can be exploited for buffer overflow attack.

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