Microsoft Windows 2000 - Trusting Domains Do Not Verify Domain Membership of SIDs in Authorization Data - 1.0

Trust relationships are created between Windows NT or Windows 2000 domains to allow users in one domain to access resources in other domains without requiring them to authenticate separately to each domain. When a user in a trusted domain requests access to a resource in a trusting domain, the trusted domain supplies authorization data in the form of a list of Security Identifiers (SIDs) that indicate the user's identity and group memberships. The trusting domain uses this data to determine whether to grant the user's request.

A vulnerability exists because the trusting domain does not verify that the trusted domain is actually authoritative for all the SIDs in the authorization data. If one of the SIDs in the list identified a user or security group that is not in the trusted domain, the trusting domain would accept the information and use it for subsequent access control decisions. If an attacker inserted SIDs of his choice into the authorization data at the trusted domain, he could elevate his privileges to those associated with any desired user or group, including the Domain Administrators group for the trusting domain. This would enable the attacker to gain full Domain Administrator access on computers in the trusting domain.