This indicates an attack attempt to exploit a Memory Corruption vulnerability in Microsoft Office Excel.
The vulnerability is due to improper handling of objects while the vulnerable software attempts to access a specially crafted excel file. An attacker can exploit this to get access to sensitive information via a crafted excel file.
Microsoft Excel 2007 Service Pack 3
Microsoft Excel 2010 Service Pack 2 (32-bit editions)
Microsoft Excel 2010 Service Pack 2 (64-bit editions)
Microsoft Excel 2013 Service Pack 1 (32-bit editions)
Microsoft Excel 2013 Service Pack 1 (64-bit editions)
Microsoft Excel 2013 RT Service Pack 1
Microsoft Word 2013 RT Service Pack 1
Microsoft Excel 2016 (32-bit edition)
Microsoft Excel 2016 (64-bit edition)
Microsoft Excel for Mac 2011
Microsoft Excel 2016 for Mac
Microsoft Office Compatibility Pack Service Pack 3
Excel Services on Microsoft SharePoint Server 2013 Service Pack 1
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems
Apply the most recent upgrade or patch from the vendor.