A remote code execution vulnerability exists in the way that DirectWrite handles objects in memory. An attacker who successfully exploited this vulnerability could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
There are multiple ways an attacker could exploit the vulnerability, such as by convincing a user to open a specially crafted document, or by convincing a user to visit an untrusted webpage.
The security update addresses the vulnerability by correcting how DirectWrite handles objects in memory.