Heap-based buffer overflow in Microsoft Excel 2007 SP2 and SP3 and 2010 Gold and SP1, Excel Viewer, and Office Compatibility Pack SP2 and SP3 allows remote attackers to execute arbitrary code via a crafted spreadsheet that triggers incorrect handling of memory during opening, aka "Excel MergeCells Record Heap Overflow Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A14738
https://exchange.xforce.ibmcloud.com/vulnerabilities/75118
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2012/ms12-030
http://www.us-cert.gov/cas/techalerts/TA12-129A.html