Microsoft Silverlight 5 before 5.1.41212.0 mishandles negative offsets during decoding, which allows remote attackers to execute arbitrary code or cause a denial of service (object-header corruption) via a crafted web site, aka "Silverlight Runtime Remote Code Execution Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-006