Microsoft Internet Explorer (mshtml.dll) - Remote Code Execution

Microsoft Internet Explorer (mshtml.dll) - Remote Code Execution

From: advisories@xxxxxxxxxxxxxxxxxxxxx

Date: 22 Mar 2006 16:19:54 -0000

Computer Terrorism (UK) :: Incident Response Centre
======================================

Security Advisory :: CT22-03-2006
-------------------------------------------

Title: Microsoft Internet Explorer (mshtml.dll) - Remote Code Execution

Organisation: Computer Terrorism (UK)
Web: www.computerterrorism.com
Advisory Date: 22nd March, 2006

Affected Software: Microsoft Internet Explorer 6.x, IE7 Beta 2
Severity: Critical
Impact: Remote System Access
Solution Status: ** UNPATCHED **

Overview:
-------------

Pursuant to the publication of the aforementioned bug/vulnerability, this document serves as a preliminary Security Advisory for users of Microsoft Internet Explorer version 6 and 7 Beta 2.

Successful exploitation will allow a remote attacker to execute arbitrary code against a fully patched Windows XP system, yielding system access with privileges of the underlying user.

Technical Narrative:
-------------------------

As per the publication, the bug originates from the use of a createTextRange() method, which, under certain circumstances, can lead to an invalid/corrupt table pointer dereference.

As a result, IE encounters an exception when trying to call a deferenced 32bit address, as highlighted by the following sniplet of code.

0x7D53C15D MOV ECX, DWORD PTR DS:[EDI]
..
0x7D53C166 CALL DWORD PTR [ECX]

Due to the incorrect reference, ECX points to a very remote, non-existent memory location, causing IE to crash (DoS). However, although the location is some what distant, history dictates that a condition of this nature is conducive towards reliable exploitation.

Proof of Concept:
-----------------------

Computer Terrorism (UK) can confirm the production of reliable proof of concept (PoC) for this vulnerability (tested on Windows XP SP2). However, until a patch is developed, we will NOT be publicly disclosing our research.

Temporary Solution:
-------------------------

Users are advised to disable active scripting for non-trusted sites until a patch is released.

Vendor Status:
--------------------

The Vendor has been informed of all aspects of this new vulnerability (including PoC), but as of the date of the document, this vulnerability is UNPATCHED.