ExploitFormatStringVuln

A hands-on demonstration of format string vulnerabilities in C — showing how improper use of printf and related functions can expose a program's memory and be leveraged for exploitation.

---

What is a Format String Vulnerability?

A format string vulnerability occurs when user-controlled input is passed directly as the format argument to functions like printf, fprintf, or sprintf — without a proper format specifier.

// Vulnerable
printf(user_input);

// Safe
printf("%s", user_input);

An attacker can supply format specifiers (e.g. %x, %s, %n) to read from or write to arbitrary memory locations on the stack.

---

Contents

Folder	Description
ReadFormatVuln/	C source and shell scripts demonstrating how to read memory via format string attacks

---

Techniques Covered

• Stack memory leaking — using %lx to dump stack values
• Arbitrary memory reads — using %s to read from a target address
• Direct parameter access — using %N$x to access specific stack positions

---

Requirements

• Linux (x86 or x86-64)
• GCC
• Basic familiarity with C and the stack

---

Usage

# Compile the vulnerable program
gcc -o main main.c

# Run the exploit script
bash exploit.sh

⚠️ Disclaimer: This repository is for educational purposes only. Do not use these techniques against systems you do not own or have explicit permission to test.

---