Software Engineering Institute

Internet Protocol version 6 (IPv6) is an IP standard that is designed to replace the Internet Protocol version 4 (IPv4). The Microsoft Teredo service is used by Microsoft Windows Vista, XP, and Server 2003 to allow clients with only IPv4 connectivity to obtain and use publicly routable IPv6 addresses.

The Teredo service must be manually enabled by an administrator in Windows XP and Server 2003. The Teredo service is enabled by default in Windows Vista, but is not activated until an application requests an IPv6 address.

The Windows firewall does not properly apply stateful packet inspection rules to incoming Teredo traffic.

Note that the Teredo service may create a tunnel through perimeter firewalls, bypassing access control lists and content inspection filtering. See RFC 4380 section 7.1 for more details.

A remote, unautheticated attacker may be able to send unsolicited and unfiltered IPv6 traffic to a vulnerable system.

Update
Microsoft has released an update to address this issue. Users are encourgaed to review Microsoft Security Bulletin MS07-038 and take appropriate action.

Disable Teredo

Disabling the Teredo service will mitigate this vulnerability. See Microsoft Security Bulletin MS07-038 for information on how to disable Teredo.