![]() A buffer overflow lets the attacker gain shell access and attempt further privilege escalation. If an integer overflow happens when you calculate the length of a buffer, you may end up with a buffer overflow.However, in some cases, integer overflows may have severe consequences: Most integer overflow conditions simply lead to erroneous program behavior but do not cause any vulnerabilities. For example, one operation may treat an integer as an unsigned one and another operation may treat exactly the same integer as a signed one, therefore interpreting the value incorrectly. In addition to typical operations such as addition, subtraction, or multiplication, integer overflows may also happen due to typecasting. When you go below the minimum value (underflow), the result usually becomes a positive number. When you go above the maximum value of the signed integer, the result usually becomes a negative number. Results can be even more unexpected for signed integers. For the above example, the result is most often 0. And, unfortunately, most languages and most compilers raise no error at all and simply perform a modulo operation, wraparound, or truncation, or they have other undefined behavior. However, what happens when you perform the calculation 4,294,967,295 + 1 and attempt to store the result that is greater than the maximum value for the integer type? It depends completely on the language and the compiler. In the case of signed integers, the most significant (first) bit usually signifies whether the integer is a positive value or a negative value. For example, space reserved for a 32-bit integer data type may store an unsigned integer between 0 and 4,294,967,295 or a signed integer between −2,147,483,648 and 2,147,483,647. In most programming languages, integer values are usually allocated a certain number of bits in memory. Integer overflows have been listed as the number 8 most dangerous software error in the most recent CWE 2019 list, mostly because they often lead to buffer overflows, which are currently the number 1 most dangerous software error according to that list. Instead of an error in the program, it usually causes the result to be unexpected. ![]() An integer overflow is a type of an arithmetic overflow error when the result of an integer operation does not fit within the allocated memory space.
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