Technical Information

Brief overview of the risk:
This vulnerability could allow an attacker to spoof an IPv4 address so that it may bypass filtering devices that rely on the source IPv4 address. The security update addresses the vulnerability by changing the manner in which the Windows TCP/IP stack checks the source IPv6 address in a tunneled ISATAP packet.
Detailed Information on the risk:

A spoofing vulnerability exists in the Microsoft Windows IPv6 stack due to the way that Windows checks the inner packet’s IPv6 source address in a tunneled ISATAP packet. An attacker who successfully exploited this vulnerability could impersonate an address to bypass edge or host firewalls. Additionally, information could be disclosed when the targeted computer replies to the message using the source IPv6 address that the attacker specified.

Further information on this exploit is available at : MS10-029