Multiple vulnerabilities have been reported in Microsoft Excel, which can be exploited by malicious people to compromise a user's system.

1) An array-indexing error when processing certain records can be exploited to corrupt memory via a specially crafted Excel file.

2) An error when parsing certain records may result in a corrupted pointer being used when opening a specially crafted Excel
file.

3) An error when parsing certain records may result in a corrupted object being used when opening a specially crafted Excel file.

4) An error when parsing certain records can be exploited to corrupt memory when opening a specially crafted Excel file.

5) A boundary error when parsing certain records can be exploited to cause a stack-based buffer overflow when opening a specially crafted Excel file.

6) An error when parsing Qsir BIFF records (0x806) may result in a corrupted pointer being used when opening a specially crafted Excel file.

7) An integer overflow error when processing the number of strings in a file can be exploited to cause a heap-based buffer overflow via a specially crafted Excel file.

Successful exploitation of the vulnerabilities may allow execution of arbitrary code.

Solution
Apply patches.
Further details available in Customer Area

Provided and/or discovered by
1) Carsten Eiram, Secunia Research.
2-4) The vendor credits Bing Liu, Fortinet.
5) TELUS Security Labs Vulnerability Research Team.
6) an anonymous person, reported via ZDI.
7) Independently reported by:
* Carsten Eiram, Secunia Research.
* Sean Larsson and Joshua Drake, VeriSign iDefense Labs.

Changelog
Further details available in Customer Area

Original Advisory
MS09-021 (KB969462, KB969661, KB969679, KB969680, KB969681, KB969682, KB969683, KB969685, KB969686, KB969737, KB971822, KB971824):
http://www.microsoft.com/technet/security/Bulletin/MS09-021.mspx

Secunia Research:
http://secunia.com/secunia_research/2009-1/
http://secunia.com/secunia_research/2009-12/

TELUS Security Labs:
http://telussecuritylabs.com/threats/show/FSC20090609-01

ZDI:
http://www.zerodayinitiative.com/advisories/ZDI-09-040/

iDefense:
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=805

Deep Links
Links available in Customer Area