![]() ![]() To get around needing the actual address, the malicious command is often padded on both sides by NOP - or no operation - computer instructions, a type of pointer. The hacker must know the address where the malicious command will reside. It then tries to recover by going to the return address, but the return address has been changed to point to the command the hacker specified. The program partially crashes because the stack overflowed. The attacker must specify a return address that points to the malicious command. Yet, overflowing the buffer with an executable command doesn't mean that the command will be executed. For instance, in a Linux environment, the command is typically EXEC("sh"), which tells the system to open a command prompt window, known as a root shell in Linux circles. ![]() Rather than enter the name, the hacker would enter an executable command that exceeds the stack size. This change alters the process's execution path and transfers control to the attacker's malicious code.įor example, suppose a program is waiting for users to enter their name. The attacker usually sets the new values to a location where the exploit payload is positioned. However, the attacker can set new values to point to an address of their choosing. The original data in the buffer includes the exploited function's return pointer - the address to which the process should go next. If the excess data is then written to the adjacent memory, it overwrites any data already there. The program attempts to store the input in a buffer that isn't large enough for the input. ![]() A threat actor can send carefully crafted input - referred to as arbitrary code - to a program. Despite being well understood, buffer overflows continue to plague software from vendors both large and small.Ī buffer overflow can occur inadvertently or when a malicious actor causes it. A classic buffer overflow is specified as CWE-120 in the CWE dictionary of weakness types. Buffer overflow always ranks high in the Common Weakness Enumeration ( CWE) and SANS Top 25 Most Dangerous Software Errors. What is a buffer overflow attack and how does one work?Įxploiting a buffer overflow allows an attacker to control or crash a process or to modify its internal variables. ![]()
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