Public Vulnerability Reports

Microsoft Windows Interactive Training Buffer Overflow Vulnerability

06.14.05

BACKGROUND

Microsoft Interactive Training is an application included with some OEM
versions of Windows XP that allows users to receive multimedia training
on a variety of software products.

DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in Microsoft
Corp.'s orun32.exe application allows attackers to execute arbitrary
code under the context of the logged-on user.

The problem specifically exists when processing a malformed .cbo file. A
typical .cbo file might have the following contents:

[Microsoft Interactive Training]
User=DEFAULT
SerialID=00000000

If a malicious user crafts a file to contain a long string in the User
field, the user-supplied value is copied to a fixed-size stack buffer.
This allows an attacker to overwrite stack memory, such as the saved
return address or a Structured Exception Handler (SEH) pointer, and gain
control of execution flow.

ANALYSIS

Exploitation of this vulnerability allows remote attackers to execute
arbitrary code under the privileges of the currently logged-on user.
Exploitation requires that an attacker convince a target user to open a
malicious .cbo file. It is a common default configuration in OEM
versions of Windows XP to allow .cbo files to be opened without
confirmation via Internet Explorer; this allows an attacker to use an
IFRAME to force the .cbo file to be opened without interaction.
Microsoft Windows Interactive Training is included only in OEM versions
of Windows XP, thus minimizing the impact of this vulnerability.

DETECTION

iDEFENSE has verified that Microsoft Interactive Training, version
3.5.0.116 on Windows XP, is vulnerable. All other versions are suspected
as vulnerable. Interactive Training is included by default in OEM
versions of Windows XP.

To determine whether a given system is vulnerable, check for the
presence of the following registry key:

HKEY_CLASSES_ROOTMITrain.Documentshellopencommand 

If this key exists and contains a value, then the system has Interactive
Training installed, and it will process .cbo files.

WORKAROUND

Do not accept or open .cbo files from untrusted sources. Consider
filtering .cbo attachments at e-mail gateways.

To prevent .cbo files from being used with Microsoft Interactive
Training, remove the .cbo entry in HKEY_CLASSES_ROOT in the Windows
Registry. To do this, save the following text into a file called
"fix.reg" and open it to modify the registry:

   Windows Registry Editor Version 5.00

   [-HKEY_CLASSES_ROOT.cbo] 

This will have the effect of disassociating .cbo files from the
Interactive Training application, which will limit functionality.
However, the application can still be used as before by manually opening
the executable and entering a username.

VENDOR RESPONSE

The vendor security advisory and appropriate patches are available at:

   http://www.microsoft.com/technet/security/Bulletin/MS05-031.mspx

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-1212 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

02/23/2005   Initial vendor notification
02/23/2005   Initial vendor response
06/14/2005   Coordinated public disclosure

CREDIT

iDEFENSE Labs is credited with this discovery.

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LEGAL NOTICES

Copyright © 2005 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
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