Adobe Reader Remote Heap Memory Corruption - Subroutine Pointer Overwrite
by Piotr Bania <bania.piotr@gmail.com>
http://www.piotrbania.com



Orginal url:  http://www.piotrbania.com/all/adv/adobe-acrobat-adv.txt
  
Severity:   Critical - Possible remote code execution.

CVE ID:    CVE-2006-5857


Time line:  03/09/2006 - Advisory sent to ADOBE PSIRT
    03/09/2006 - Initial Vendor Response
    11/09/2006 - Vendor confirms the vulnerability.
    09/01/2007 - Security Bulletin ready, advisory
           released.


Software affected:   Adobe Reader 7.0.8 and earlier - all platforms.

      Tested on:
      * Adobe Reader 7.0.8 and 7.0.3 (Windows)
      * Adobe Reader 7.0.8 on (LINUX )
  


I.  BACKGROUND

Adobe Reader is the most popular program for viewing documents in
Adobe Portable Document Format (PDF). More information at:
http://www.adobe.com/products/acrobat/.



II. DESCRIPTION


The problem exists when the Adobe product is trying to render
a specially crafted PDF file.

  
Take a look a this code snipet:

----// SNIP SNIP //-------------------------------------------------
0:000> u 08009d3f
CoolType+0x9d3f:
08009d3f 83e904           sub     ecx,0x4
08009d42 890da07a1d08     mov     [CoolType!CTCleanup+0xb393b 081d7aa0)],ecx
08009d48 ffb49070feffff   push    dword ptr [eax+edx*4-0x190]
08009d4f 8b09             mov     ecx,[ecx]
08009d51 51               push    ecx
08009d52 ff506c           call    dword ptr [eax+0x6c] ; (*)
08009d55 59               pop     ecx
08009d56 59               pop     ecx
----// SNIP SNIP //-------------------------------------------------


Instruction at 0x08009d52 call the location which address is stored at
[eax+0x6c]. Value of the eax points somewhere inside the allocated
heap memory block, as shown here:

----// SNIP SNIP //-------------------------------------------------
...
K: 199 -> [*] HeapAlloc(0x3E0000,0x0,0x4(4))=0x16F6FF8 end at: 0x16F6FFC
K: 200 -> [*] HeapAlloc(0x3E0000,0x0,0x4F4(1268))=0x16F6958 end at:
0x16F6E4C
K: 201 -> [*] HeapAlloc(0x3E0000,0x0,0xFE30(65072))=0x16F6E58 end at:
0x1706C88
K: 202 -> [*] HeapAlloc(0x3E0000,0x0,0x304(772))=0x1706C90 end at: 0x1706F94
K: 203 -> [*] HeapAlloc(0x3E0000,0x0,0xFE24(65060))=0x1706FA0 end at:
0x1716DC4 <- THIS ONE
----// SNIP SNIP //-------------------------------------------------

[EAX+0x6c] points to 0x222C offset from begining of the last heap memory
block.


When specially badly created PDF file is being render, there exist a
possibility to cause a memory corruption, which leads to the overwrite
of the subroutine address stored at [eax+0x6c].

  
Here's the debugger snipet, after calling overwritten [eax+0x6c] (note
the heap base block is different then previously mentioned, its just
another independent session):

----// SNIP SNIP //-------------------------------------------------
(25a0.2170): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=016f4320 ebx=00000000 ecx=baadf00d edx=00000069 esi=016f4ab9
edi=016f14b4 eip=baadf00d esp=0012deec ebp=0012df80 iopl=0
nv up ei pl nz na pe nc
cs=001b  ss=0023  ds=0023  es=0023  fs=0038  gs=0000
efl=00010202
*** ERROR: Symbol file could not be found.  Defaulted to export symbols
for C:\Program Files\Adobe\Acrobat 7.0\Reader\CoolType.dll -
  
baadf00d ??               ???
----// SNIP SNIP //-------------------------------------------------  
The attacker can control EIP register, this may lead to a potencial code
exection in context of current user.
  
  
III. IMPACT

Successful exploitation may allow the attacker to run arbitrary code in
context of user running Adobe Reader.


IV. VENDOR RESPONSE

All pathes are available, via auto-update or
http://www.adobe.com/go/getreader/

  
V.  POC CODE

Due to severity of this vulnerability i will not disclose any POC codes.

  
best regards,
pb


-- 
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Piotr Bania - <bania.piotr@gmail.com> - 0xCD, 0x19
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