An elevation of privilege vulnerability exists when Windows improperly handles calls to Win32k.sys.

An attacker who successfully exploited this vulnerability could run arbitrary code in the security context of the local system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

To exploit this vulnerability, an attacker would first have to log on to the system. An attacker could then run a specially crafted application that could exploit the vulnerability and take control over an affected system.

The update addresses the vulnerability by correcting how Windows handles calls to Win32k.

https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2018-8589#ID0EGB