Buffer Overflow Exploitation Basics

What is Buffer Overflow?

Occurs when a program writes more data to a buffer than it can hold. The overflowing data overwrites adjacent memory regions.

Stack-Based Overflows

Target the call stack. The return address (EIP/RIP) can be overwritten with attacker-controlled data.

void vulnerable(char *input) {
    char buf[64];
    strcpy(buf, input); // no bounds checking!
}

Mitigations

ASLR, NX/DEP, and stack canaries are modern defenses. Use safe functions (strncpy, snprintf) and compiler protections.