[NT] Microsoft Excel Chart AxesSet Invalid Array Index Vulnerability (MS08-043)

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Microsoft Excel Chart AxesSet Invalid Array Index Vulnerability (MS08-043)


Microsoft <http://office.microsoft.com/excel/> Excel is "the spreadsheet
application that is included with Microsoft Corp.'s Office productivity
software suite". Remote exploitation of an invalid array indexing
vulnerability in Microsoft Corp.'s Excel could allow an attacker to
execute arbitrary code with the privileges of the current user.


Vulnerable Systems:
* Office 2000 SP-3 fully patched as of March 2008

This issue exists in the handling of "AxesSet" records within a chart
embedded in a spreadsheet. This record is typically used for setting the
location and size of a set of axes on a chart. This particular record type
is not included in Microsoft's official documentation for the Excel file
format. However, the freely available source code for OpenOffice
implements this record type.

When processing this record, Excel does not validate a value that is used
as an index into the array of chart axes. By crafting an Excel spreadsheet
(XLS) that contains an out-of-bounds array value, an attacker can cause
memory corruption. This leads to a potentially exploitable condition.

Exploitation allows an attacker to execute arbitrary code in the context
of the currently logged-on user. To exploit this vulnerability, the
attacker must persuade a user to open a specially crafted Excel (XLS)

Likely attack vectors include sending the file as an e-mail attachment or
linking to the file on a website. By default, systems with Office 2000
installed will open Office documents, including Excel spreadsheet files,
from websites without prompting the user. This allows attackers to exploit
this vulnerability without user interaction. Later versions of Office do
not open these documents automatically unless the user has chosen this

Using the Office Document Open Confirmation Tool for Office 2000 can
prevent Office files on web sites from opening automatically. Use of this
tool is highly recommended for users still using Office 2000.

Vendor response:
Microsoft has officially addressed this vulnerability with Security
Bulletin MS08-043. For more information, consult their bulletin at the
following URL:

CVE Information:

Disclosure timeline:
03/27/2008 - Initial vendor notification
03/31/2008 - Initial vendor response
08/12/2008 - Coordinated public disclosure


The information has been provided by
<mailto:idlabs-advisories@xxxxxxxxxxxx> iDefense Labs Security Advisories.
The original article can be found at:


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