EDUCBA Logo

EDUCBA

MENUMENU
  • Explore
    • EDUCBA Pro
    • PRO Bundles
    • Featured Skills
    • New & Trending
    • Fresh Entries
    • Finance
    • Data Science
    • Programming and Dev
    • Excel
    • Marketing
    • HR
    • PDP
    • VFX and Design
    • Project Management
    • Exam Prep
    • All Courses
  • Blog
  • Enterprise
  • Free Courses
  • Log in
  • Sign Up
Home Software Development Software Development Tutorials Software Development Basics What is Buffer Overflow?
 

What is Buffer Overflow?

Priya Pedamkar
Article byPriya Pedamkar

Updated March 15, 2023

What is Buffer Overflow?

 

 

Introduction to Buffer Overflow

Buffer Overflow (or Buffer Overrun) is a state in which a computer application attempts to store more data in the buffer memory than its size permits. This can result in data being stored in adjacent storage, potentially overwriting existing data and leading to data loss or even a system crash. It is a common programming mistake and hackers often exploit this vulnerability to gain access to unsolicited data.

Watch our Demo Courses and Videos

Valuation, Hadoop, Excel, Mobile Apps, Web Development & many more.

 

What’s Buffer Memory?

A buffer memory, also known as a buffer, is a sequential portion of the RAM that temporarily holds data while it is being transferred from one device to another, typically an input or output device. It compensates for differences in the speeds at which the devices operate. For example, while the latest i7 processor can execute a print command in nanoseconds, an outdated printer may not have such a fast processor. Therefore, the documents are held in the buffer memory and transferred to the printer at a speed it can accept. This frees up the CPU’s RAM for other tasks.

Buffer Overflow Attack

Once a vulnerability has been identified in the system, hackers are bound to exploit it and launch attacks through a buffer overflow. How does a hacker execute such an attack, and what are the consequences?

In a buffer overflow attack, the extra data includes instructions that are intended to trigger damaging activities such as corrupting files, changing data, sending private information across the internet, etc. An attacker injects surplus data into the buffer by taking advantage of any program that is waiting for certain user input.

Buffer overflow attacks can be primarily classified into two types:

  • Stack-based: When the attack is on stack-based memory allocation. This is simpler to exploit and thus more susceptible to attacks.
  • Heap-based: When the attack is on heap-based memory allocation. This is not easy to exploit and thus far less frequent.

The languages most vulnerable to buffer overflow attacks are C, C++, Fortran, and Assembly. They use stack-based memory allocation techniques.

Buffer Overflow: The Cure

Once data has been corrupted, there is no simple cure to restore it to its original state. Moreover, the intensity of the attack largely determines the appropriate course of action. If the attack is small-scale and only affects a portion of an isolated machine’s memory, a simple system format may be sufficient to remedy the situation. However, if the attack is widespread and has compromised data across multiple machines, formatting the entire network will not be effective unless the program injecting the malicious code is fixed.

Prevention is Better than Cure

It is the responsibility of developers to check for buffer overflows in our code. Handling buffer overflows in the code itself can prevent the security of the system from being prone to such attacks.

There are some simple precautionary steps that can help prevent buffer overflows:

  • Using exception handling to detect buffer overflows and prevent code execution in the event of one.
  • Allocate large enough size to buffers to properly handle un-intended large volumes of data.
  • Avoid using library functions or third-party methods that are not bound-checked for buffer overflows. Common examples of such functions to avoid are gets(), scanf(), strcpy(), especially in C/C++ language.
  • Code testing should account for such vulnerabilities and rigorously test the code to identify and fix bugs that may lead to overflow.
  • Modern programming languages, operating systems, and code compilers have evolved to automatically detect buffer overflows and stop the command execution in such cases. This has become the most reliable way to detect buffer overflows automatically.

Try it Yourself

Disclaimer: The following program is for demonstration purposes only and should not serve to cause harm in any way. Any resemblance to malicious code is purely coincidental. Additionally, modern operating systems come with buffer-attack-preventive measures.

Below is a C program that could potentially cause a buffer overrun. The choice of language is C because more advanced programming languages have been developed to deal with buffer overruns during compile time. However, even modern C compilers have certain checks in place to avoid detecting buffer overflows. If such an overflow were to occur, you would receive an error message indicating a buffer overrun detection.

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
char mybuffer[8];
// copy the user input to mybuffer, without any bound checking
printf("Storing user input to mybuffer...\n");
strcpy(mybuffer, argv[1]);
printf("mybuffer content= %s\n", mybuffer);
return 0;
}

Output:

output of buffer overflow

What happens when the program receives the command-line argument “123456789”? The compiler will detect the buffer overflow, causing the program to generate an error. Modern compilers and operating systems have an additional layer of protection in the form of variables called “Canaries”. These variables are initialized to certain values during compile time and stored in adjacent memory units to the buffer. When the buffer overflows, the extra data flows into the adjacent memory and corrupts the value of the Canaries. As soon as a corrupt Canary comes under detection, the system aborts the execution.

Another example in C++ Language:

Code:

#include <iostream>
using namespace std;
int main()
{
char buf[8];
cin>>buf;
return 0;
}

Input: 123456789

Output:

c# example

Conclusion

Buffer overflow makes a system vulnerable to hackers and allows them to take control of the system. Buffer handling is paramount during the writing and testing of the code, as it ensures the code is secure and immune to attacks.

Recommended Articles

Here are some further articles for increasing understanding:

  1. What is JavaScript?
  2. What Is Django?
  3. SQL Developer
  4. What Is Azure?

Primary Sidebar

Footer

Follow us!
  • EDUCBA FacebookEDUCBA TwitterEDUCBA LinkedINEDUCBA Instagram
  • EDUCBA YoutubeEDUCBA CourseraEDUCBA Udemy
APPS
EDUCBA Android AppEDUCBA iOS App
Blog
  • Blog
  • Free Tutorials
  • About us
  • Contact us
  • Log in
Courses
  • Enterprise Solutions
  • Free Courses
  • Explore Programs
  • All Courses
  • All in One Bundles
  • Sign up
Email
  • [email protected]

ISO 10004:2018 & ISO 9001:2015 Certified

© 2025 - EDUCBA. ALL RIGHTS RESERVED. THE CERTIFICATION NAMES ARE THE TRADEMARKS OF THEIR RESPECTIVE OWNERS.

EDUCBA

*Please provide your correct email id. Login details for this Free course will be emailed to you
Loading . . .
Quiz
Question:

Answer:

Quiz Result
Total QuestionsCorrect AnswersWrong AnswersPercentage

Explore 1000+ varieties of Mock tests View more

EDUCBA

*Please provide your correct email id. Login details for this Free course will be emailed to you
EDUCBA
Free Software Development Course

Web development, programming languages, Software testing & others

By continuing above step, you agree to our Terms of Use and Privacy Policy.
*Please provide your correct email id. Login details for this Free course will be emailed to you
EDUCBA

*Please provide your correct email id. Login details for this Free course will be emailed to you

EDUCBA Login

Forgot Password?

🚀 Limited Time Offer! - 🎁 ENROLL NOW