Microsoft has released several security alerts for Microsoft Internet Explorer. Here are four of them:
HTTPS Proxy Vulnerability (CAN-2005-2830)
File Download Dialog Box Manipulation Vulnerability (CAN-2005-2829)
COM Object Instantiation Memory Corruption Vulnerability (CAN-2005-2831)
Mismatched Document Object Model Objects Memory Corruption Vulnerability (CAN-2005-1790)
This can cause problems ranging from attackers reading web addresses sent to a proxy server to running malicious code on your hosts to gain admin access.
MS05-055Vulnerability in Windows Kernel Allows Elevation of Privilege (908523)http://www.microsoft.com/technet/security/bulletin/MS05-055.mspx
This one allows attackers to escalate or gain higher privleges than allowed an example would be a user with no rights gaining administrative control of the machine. It is possible to change kernel memory with this vulnerability. This can lead to remote code execution as well.