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Fortinet Security Advisory: FSA-2006-09



Fortinet Security Advisory: FSA-2006-09

Microsoft Excel Formula Size Stack Overflow

Advisory Date      : March 14, 2006                     
Reported Date      : January 24, 2006
Vendor             : Microsoft                  
Affected Products  : Microsoft Excel 2003 Chinese Version
                     Windows XP Home Edition Chinese Version and 
                     possible all versions of Microsoft Excel.
Severity           : High
Reference          : 
http://www.microsoft.com/technet/security/Bulletin/MS06-012.mspx
                     http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0029
                     http://www.securityfocus.com/bid/15780
                   
Description        :  Fortinet Security Research Team (FSRT) has discovered a 
Improper Stack  Overflow Vulnerability in the Microsoft Excel software. This 
vulnerability is due to Microsoft Excel's manipulation of opcode 0x0218, when 
provided with a large Formula Size, it will cause a stack overflow. An remote 
attacker could construct a .xls file and put it on controlled web site. When 
the user opens the .xls file with Microsoft Internet Explorer, the browser will 
call Microsoft Excel to open the .xls file automatically, and this will cause 
Microsoft Excel to crash. If excel file is specially crafted, it may allow 
attackers to execute arbitrary code on the affected system.

Impact             : Execution of arbitrary code leading to system compromise.

Solution           : Microsoft has released a update for this vulnerability, 
which is available for downloading from Microsoft web site, see reference. 

Fortinet Protection: FortiGate series of security systems have been updated to 
detect exploits targeting this vulnerability.

Acknowledgment     : Dejun Meng of Fortinet Security Research team found this 
vulnerability. 

Disclaimer         : Although Fortinet has attempted to provide accurate 
information in these materials, Fortinet assumes no legal responsibility for 
the accuracy or completeness of the information. More specific information is 
available on request from Fortinet. Please note that Fortinet's product 
information does not constitute or contain any guarantee, warranty or legally 
binding representation, unless expressly identified as such in a duly signed 
writing.