Microsoft Excel 2002 SP3, Office 2004 and 2008 for Mac, and Open XML File Format Converter for Mac obtain a certain length value from an uninitialized memory location, which allows remote attackers to trigger a buffer overflow and execute arbitrary code via a crafted Excel file, aka "Excel Data Initialization Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12618
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2011/ms11-021
http://www.vupen.com/english/advisories/2011/0940
http://www.us-cert.gov/cas/techalerts/TA11-102A.html