A buffer overflow is a type of exploit that allows hackers to get access to the memory of a computer. A buffer is a temporary storage space in which data can be stored while processing it. When a hacker creates a buffer overflow, they are able to send more data than the size of the buffer allows, and thus overwrite the data in other parts of the computer’s memory.
This can cause problems for web servers because they use buffers to store information about clients’ requests before sending them back to the client. If an attacker were to create a buffer overflow on their own computer and then connect to another computer (in this case, a web server), their request would take precedence over others waiting in line because it would be given priority over other requests due to its higher status within the system.
Because of this, hackers can use buffer overflows as part of attacks against web servers.
What Is A Buffer Overflow And How Is It Used Against A Web Server
Buffers are memory storage regions that temporarily hold data while it is being transferred from one location to another. A buffer overflow (or buffer overrun) occurs when the volume of data exceeds the storage capacity of the memory buffer. As a result, the program attempting to write the data to the buffer overwrites adjacent memory locations.
For example, a buffer for log-in credentials may be designed to expect username and password inputs of 8 bytes, so if a transaction involves an input of 10 bytes (that is, 2 bytes more than expected), the program may write the excess data past the buffer boundary.
Buffer overflows can affect all types of software. They typically result from malformed inputs or failure to allocate enough space for the buffer. If the transaction overwrites executable code, it can cause the program to behave unpredictably and generate incorrect results, memory access errors, or crashes.
Buffer overflow example
What is a Buffer Overflow Attack
Attackers exploit buffer overflow issues by overwriting the memory of an application. This changes the execution path of the program, triggering a response that damages files or exposes private information. For example, an attacker may introduce extra code, sending new instructions to the application to gain access to IT systems.
If attackers know the memory layout of a program, they can intentionally feed input that the buffer cannot store, and overwrite areas that hold executable code, replacing it with their own code. For example, an attacker can overwrite a pointer (an object that points to another area in memory) and point it to an exploit payload, to gain control over the program.
Types of Buffer Overflow Attacks
Stack-based buffer overflows are more common, and leverage stack memory that only exists during the execution time of a function.
Heap-based attacks are harder to carry out and involve flooding the memory space allocated for a program beyond memory used for current runtime operations.
What Programming Languages are More Vulnerable?
C and C++ are two languages that are highly susceptible to buffer overflow attacks, as they don’t have built-in safeguards against overwriting or accessing data in their memory. Mac OSX, Windows, and Linux all use code written in C and C++.
Languages such as PERL, Java, JavaScript, and C# use built-in safety mechanisms that minimize the likelihood of buffer overflow.
How to Prevent Buffer Overflows
Developers can protect against buffer overflow vulnerabilities via security measures in their code, or by using languages that offer built-in protection.
In addition, modern operating systems have runtime protection. Three common protections are:
- Address space randomization (ASLR)—randomly moves around the address space locations of data regions. Typically, buffer overflow attacks need to know the locality of executable code, and randomizing address spaces makes this virtually impossible.
- Data execution prevention—flags certain areas of memory as non-executable or executable, which stops an attack from running code in a non-executable region.
- Structured exception handler overwrite protection (SEHOP)—helps stop malicious code from attacking Structured Exception Handling (SEH), a built-in system for managing hardware and software exceptions. It thus prevents an attacker from being able to make use of the SEH overwrite exploitation technique. At a functional level, an SEH overwrite is achieved using a stack-based buffer overflow to overwrite an exception registration record, stored on a thread’s stack.
Security measures in code and operating system protection are not enough. When an organization discovers a buffer overflow vulnerability, it must react quickly to patch the affected software and make sure that users of the software can access the patch.
See how Imperva DDoS Protection can help you with buffer overflow attacks.
How Imperva Helps Mitigate Buffer Overflow Attacks
The Imperva security solution is deployed as a gateway to your application and provide out-of-the-box protection for buffer overflow attacks. It does so by blocking illegal requests that may trigger a buffer overflow state, preventing them from reaching your applications.
In addition to protecting against buffer overflow attacks, Imperva provides multi-layered protection to make sure websites and applications are available, easily accessible and safe. The Imperva application security solution includes:
- DDoS Protection—maintain uptime in all situations. Prevent any type of DDoS attack, of any size, from preventing access to your website and network infrastructure.
- Web Application Firewall—permit legitimate traffic and prevent bad traffic. Safeguard your applications on-premises and at the edge with an enterprise‑class cloud WAF.
- Bot Management– get full visibility and control over human, good bot, and bad bot traffic to your website and API.
- Account Takeover Protection—uses an intent-based detection process to identify and defends against attempts to take over users’ accounts for malicious purposes.
- API Security—protects APIs by ensuring only desired traffic can access your API endpoint, as well as detecting and blocking exploits of vulnerabilities.
- RASP—keep your applications safe from within against known and zero‑day attacks. Fast and accurate protection with no signature or learning mode.
- Attack Analytics—mitigate and respond to real security threats efficiently and accurately with actionable intelligence across all your layers of defense.
types of buffer overflow attacks
Many different buffer overflow attacks use different strategies and target different pieces of code. Below are the best-known buffer overflow attacks:
- Stack overflow attack – This is the most common type of buffer overflow attack and involves buffer overflow in the call stack.
- Heap overflow attack – This type of attack targets data in the open memory pool known as the heap.
- Integer overflow attack – When an integer overflows, an arithmetic operation results in an integer (integer) that is too large to store the integer type; this may result in a buffer overflow.
- Unicode overflow – Unicode overflow creates a buffer overflow by inserting Unicode characters into the expected input of ASCII characters. (ASCII and Unicode encoding standards that allow computers to display text. For example, the ASCII number 97 stands for the letter “a.” Although ASCII codes only cover Western language characters, Unicode is the world in which characters can be created. in almost any written language. If more other characters are available in Unicode, many Unicode characters are larger than most ASCII characters.
Stack Overflow Attack:
The stack is a LIFO (Last In First Out) data structure. It supports two operations: PUSH and POP. The PUSH operation is used to specify the value of the steel, and the POP operation is used to extract the value of the steel. If the data placed on the stack is corrupted, they will overwrite the adjacent memory location and affect the data or pointer already stored by the other program. Steel overflow is an old vulnerability that uses stacked memory that only exists during runtime. The vulnerability is usually in C or C ++ because we are free to use the pointer in those languages. An attacker or hacker could take advantage of this vulnerability to exploit the system by manipulating data or creating a pointer to run malicious code.
Heap Overflow Attack:
The heap overflow occurs when a piece of memory is assigned to the heap and the data is written to that memory without the data being checked. This may result in some critical data structures in the heap, such as heap headers, or any heap-based data, such as dynamic object pointers, which can overwrite the virtual function table.
Integer Overflow Attack:
Integer overflow is a type of arithmetic overflow error where the result of an integer operation does not lie in the allocated memory space. Instead of a program error, it usually results in an unexpected result. In most programming languages, integer values usually have a certain number of bits in memory.
For example, the space reserved for a 32 – bit integer data type may be an unsigned integer between 0 and 4,294,967,295, or a signed integer between −2,147,483,648 and 2,147,483,647. However, what happens if you calculate 4,294,967,295 + 1 and try to store the result that exceeds the maximum value for the whole type? Because most languages and most compilers make no mistakes at all and only perform a modulo, accept, or truncate operation, it only crashes and puts you at risk of attack.
Most integer overflow conditions simply lead to erroneous program behavior but do not cause any vulnerabilities. However, in some cases, integer overflows may have severe consequences like manipulating financial calculation, causing a customer to receive debit instead of credit or something alike.
Unicode Overflow:
Unicode strings have been created to ensure that all languages from any country can be used without transcription problems. For example, Arabic characters are different from English characters. He realized that such characters could not be converted according to the ASCII codes we know. Any character can be used with Unicode strings. And the Unicode schema allows the user to take advantage of the program by typing Unicode characters in input that expects ASCII characters. It simply provides input that surpasses the maximum limit to make a buffer overflow with uncertain characters of Unicode where the program is expecting ASCII input.