Https- Bit.ly Crackfire Access

The binary is compiled PIE, so we need to of _start (found via readelf -s crackfire | grep _start → 0x4006f0 ) to get the load address:

Challenge type: Binary exploitation (pwn) – 64‑bit Linux Difficulty: Medium / Hard (depends on the exact variant) Points: 500 (CTF typical) TL;DR – The binary is a simple “crack‑the‑code” game that reads a user‑supplied string, checks it against a secret flag stored in the binary, and then prints “Access granted!” on success. The binary contains a classic format‑string vulnerability that lets us leak the address of the secret and later overwrite the check function’s return address to jump to win . By combining an info‑leak with a one‑shot ret2win payload we obtain the flag. Below is a step‑by‑step walkthrough that shows the thought process, the tools used, and the final exploit script (Python + pwntools). Feel free to copy the script and adapt it for the exact binary you downloaded from the short link. 1. Getting the binary The challenge link ( https://bit.ly/crackfire ) resolves to a zip file containing: https- bit.ly crackfire

%p %p %p %p %p %p %p %p %p %p %p %p %p %p %p %p Output (truncated): The binary is compiled PIE, so we need

from pwn import *