Microsoft Communicator 2007 R2, Lync 2010, Lync 2010 Attendee, and Lync Server 2013 do not properly handle objects in memory, which allows remote attackers to execute arbitrary code via an invitation that triggers access to a deleted object, aka "Lync RCE Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A15952
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2013/ms13-041