A remote code execution vulnerability exists in Windows when the iSNS Server service fails to properly validate input from the client, leading to an integer overflow. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the SYSTEM account.
An attacker could exploit the vulnerability by creating a specially crafted application to connect to the iSNS Server and then issue malicious requests to it.
The update addresses the vulnerability by modifying how the iSNS Server service parses requests.