Technical Information

Brief overview of the risk:
This security update resolves vulnerabilities in Microsoft Silverlight. The most severe of the vulnerabilities could allow remote code execution if Microsoft Silverlight incorrectly handles certain open and close requests that could result in read- and write-access violations. To exploit the vulnerability, an attacker could host a website that contains a specially crafted Silverlight application and then convince a user to visit a compromised website. The attacker could also take advantage of websites containing specially crafted content, including those that accept or host user-provided content or advertisements.
Detailed Information on the risk:
In the web-browsing scenario, an attacker who successfully exploited this vulnerability could obtain the same permissions as the currently logged-on user. If a user is logged on with administrative user rights, an attacker could take complete control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. The update addresses the vulnerability by correcting how Microsoft Silverlight handles certain open and close web requests.Further information on this exploit is available at : MS15-129