DirectWrite in Microsoft Windows Vista SP2, Windows Server 2008 SP2, R2, and R2 SP1, and Windows 7 Gold and SP1 does not properly render Unicode characters, which allows remote attackers to cause a denial of service (application hang) via a (1) instant message or (2) web site, aka "DirectWrite Application Denial of Service Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A14807
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2012/ms12-019