This article guides viewers through the methodology of scanning, identifying vulnerabilities, and exploiting a PHP-based server using the TryHackMe “Agent T” room.
Initial Scanning Strategy
The attack begins with an Nmap scan, revealing a single open port running a PHP CLI server with version 8.1.0-dev, suggesting potential vulnerabilities.
Exploiting PHP 8.1.0-dev
We identify an exploit for this version involving a backdoor triggered via the User-Agent HTTP header, allowing remote code execution.
Bypassing Authentication:
The admin dashboard was accessible without authentication, a rare and risky configuration in real-world scenarios.
Burp Suite for Recon
We then use Burp Suite to intercept HTTP traffic and uncover the server’s PHP version from response headers, bypassing the need for version detection through Nmap.
Python Exploit Execution
A Python script tailored to exploit PHP 8.1.0-dev is downloaded, configured with the server’s URL, and executed, ultimately granting root access to the machine.
Privilege Escalation & Flag Capture
After successful exploitation, root access is confirmed and the final flag is located and displayed, completing the challenge.
Quick Tech Facts
PHP Version 8.1.0-dev: This is crucial because it contained a known backdoor, exploitable via a simple User-Agent manipulation, highlighting the risk of using dev or early-release versions in production.
Port 8080: Standard proxy configuration used in Burp Suite to capture requests and responses—an essential part of the reconnaissance process.
March 28, 2021: The date when the vulnerable PHP version was released, underlining the importance of timely updates and patch management.
Why PHP 8.1.0-dev is particularly dangerous to run on live servers
PHP 8.1.0-dev is extremely risky to deploy on production systems because it was released with a backdoor vulnerability. This backdoor was accidentally introduced and quickly discovered and removed, but during the window of its availability, attackers could exploit it by sending a specially crafted User-Agent header.
Here’s why it’s dangerous:
- Remote Code Execution: The exploit enables attackers to execute arbitrary code on the server by simply modifying an HTTP request’s User-Agent field—no need for authentication or complex payloads.
- Backdoor Built-in: The vulnerability was baked into the core of this dev version, not from third-party plugins or misconfigurations.
- Lack of Server Hardening: As shown in the video, the server openly reveals its PHP version through HTTP headers, which makes it easy for hackers to match known exploits to the target.
- Early Release Status: “Dev” versions are for development and testing only—they are not stable or secure enough for real-world deployment, and using them publicly opens doors for exploits that haven’t been fully audited.
How attackers can bypass login pages and gain direct access to admin dashboards?
The target system’s admin dashboard is directly accessible without any authentication, which is a significant vulnerability. Here’s how this plays into bypassing login pages:
- No Login Requirement: Upon navigating to the target IP via a browser, the hacker is taken straight into the admin dashboard—a situation that’s described as “unlikely to happen in the real world” but very risky.
- Misconfigured Access Control: The lack of authentication implies a severe misconfiguration. Admin interfaces should always be protected by credentials and ideally by additional controls like IP whitelisting or 2FA.
- Testing & CTF Environments: While this setup may be intentional for Capture The Flag (CTF) scenarios like TryHackMe, in real-world applications, admin areas should be hidden or protected, not publicly exposed.
- Reconnaissance Value: Gaining access to the admin panel gives attackers critical insights into the server’s setup, features, and possibly even file upload or command execution functions—all without needing to crack a password.
TryHackMe Agent T | Room Answers
What is the flag?
flag{4127d0530abf16d6d23973e3df8dbecb}
