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Buffer overflow vulnerability9/14/2023 ![]() ![]() When a jump or branch is encountered, the instruction pointer's value is altered to point to the new location in memory, where sequential fetching of instructions begins anew. ![]() These branches and jumps are caused by if–then conditions, loops, subroutines, goto statements, and related conditions in the program. The CPU continues stepping through memory, grabbing and executing instructions sequentially, until some type of branch or jump is encountered. The next instruction is then fetched and run. The CPU executes this instruction, and the Instruction Pointer is incremented to point to the next instruction. The CPU grabs one program instruction from memory by using the Instruction Pointer to refer to a location in memory where the instruction is located within the given segment of code. The CPU contains a very special register called the Instruction Pointer, which tells it where to grab the next instruction for the running program. The whole program itself is just a bunch of bits in the computer's memory, in the form of a series of instructions for the processor. When running a program, your machine's Central Processing Unit (CPU) fetches instructions from memory, one by one, in sequence. How does this occur? Consider Figure 7.2, which highlights the relationship of a system's processor and memory during execution. Right now, if your computer is booted up, it is processing millions of computer instructions per second, all written in machine language code. To understand how stack-based buffer overflow attacks work, we first need to review how a computer runs a program. There are a variety of buffer overflow types, but we look at two of the most common and popular: stack-based buffer overflows and heap overflows. ![]() Based on this mistake, an attacker can send more data than is anticipated and break out of the bounds of certain variables, possibly altering the flow of the target program or even tweaking the value of other variables. In essence, these flaws are a result of sloppy programming, with a developer who forgets to create code to check the size of user input before moving it around in memory. The buffer that is overflowed is really just a variable used by the target program. Attackers love this ability to execute commands on a target computer.īuffer overflow vulnerabilities are based on an attacker sending more data to a vulnerable program than the original software developer planned for when writing the code for the program. Depending on the privileges I'd have to run these commands, I could add accounts, access a command prompt, remotely control the GUI, alter the system's configuration. Imagine if I could execute one or two commands on your valuable server, workstation, or palmtop computer. Since the publication of this paper, the number of buffer overflow vulnerabilities discovered continues to skyrocket, with several brand new flaws and exploits to take advantage of them released almost every single day.īy exploiting vulnerable applications or operating systems, attackers can execute commands of their choosing on target machines, potentially taking over the victim machines. You can find this detailed and well-written paper, which is still an invaluable read even today, at Before this paper, buffer overflows were an interesting curiosity, something we talked about but seldom saw in the wild. Although the infosec community has known about buffer overflows for decades, this type of attack really hit the big time in late 1996 with the release of a seminal paper on the topic called "Smashing the Stack for Fun and Profit" by Aleph One. Counter Hack Reloaded: A Step-by-Step Guide to Computer Attacks and Effective Defenses, 2nd Editionīuffer overflows are extremely common today, and offer an attacker a way to gain access to and have a significant degree of control over a vulnerable machine. ![]()
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