STA Threads Lose Thread Token

If a Single Threaded Apartment (STA) thread sets a thread token on its apartment thread, it may lose this token unexpectedly. As a result, secure calls to open files, databases, and so on, can fail. This behavior is exhibited only by STA servers; MTA servers are unaffected by this problem.

This problem is caused by a bug in the COM/RPC runtime that causes it to incorrectly revert the thread token after a call was dispatched to the STA.

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

COM server processes may set thread tokens on their threads for various reasons. Secure calls from such threads will use the thread token in the access checks performed by the operating system. If these threads also happen to host STA objects, the token can be lost because of the above bug. Secure calls from the threads will then use the process token for access checks, and this can lead to different results from the first case. The problem usually manifests as unexpected security failures in secure accesses made by such threads.