Secunia Research: Microsoft Excel rtWnDesk Record Memory Corruption Vulnerability

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                     Secunia Research 15/08/2007

 - Microsoft Excel rtWnDesk Record Memory Corruption Vulnerability -

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Table of Contents

Affected Software....................................................1
Severity.............................................................2
Vendor's Description of Software.....................................3
Description of Vulnerability.........................................4
Solution.............................................................5
Time Table...........................................................6
Credits..............................................................7
References...........................................................8
About Secunia........................................................9
Verification........................................................10

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1) Affected Software 

Microsoft Office Excel 2000, XP, 2003, 2003 Viewer, 2004 for Mac.

NOTE: Other versions may also be affected.

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2) Severity 

Rating: Highly critical
Impact: System access
Where:  From remote

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3) Vendor's Description of Software 

"Organize, analyze and present your data with precision and panache.".

Product Link:
http://office.microsoft.com/en-us/excel/

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4) Description of Vulnerability

Secunia Research has discovered a vulnerability in Microsoft Excel,
which can be exploited by malicious people to compromise a user's
system.

The vulnerability is caused due to an error when validating an index
value in the rtWnDesk record and can be exploited to corrupt memory
via a specially crafted Excel Workspace (XLW) file. A negative index
value will cause a pointer to reference memory outside of an
allocated buffer. Subsequent records will read and write to the user
controlled location.

Successful exploitation may allow execution of arbitrary code.

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5) Solution 

Install the patch released with MS07-044 (KB940965):
http://www.microsoft.com/technet/security/Bulletin/MS07-044.mspx

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6) Time Table 

17/07/2007 - Vendor notified.
18/07/2007 - Vendor response.
15/08/2007 - Public disclosure.

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7) Credits 

Discovered by Dyon Balding, Secunia Research.

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8) References

The Common Vulnerabilities and Exposures (CVE) project has assigned 
CVE-2007-3890 for the vulnerability.

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9) About Secunia

Secunia offers vulnerability management solutions to corporate
customers with verified and reliable vulnerability intelligence
relevant to their specific system configuration:

http://corporate.secunia.com/

Secunia also provides a publicly accessible and comprehensive advisory
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Secunia believes that it is important to support the community and to
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security and reliability of software in general:

http://corporate.secunia.com/secunia_research/33/

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http://secunia.com/secunia_security_advisories/ 

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10) Verification 

Please verify this advisory by visiting the Secunia website:
http://secunia.com/secunia_research/2007-65/

Complete list of vulnerability reports published by Secunia Research:
http://secunia.com/secunia_research/

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