Microsoft Warns of NT 4.0 Bug

Microsoft Corp. has released a tool that installs tighter permissions on a Windows NT 4.0 registry key. The default permissions could allow a malicious user who can interactively log onto an NT 4.0 machine to compromise the cryptographic keys of other users who subsequently log onto the same machine.

The vulnerability involves a registry key used by the CryptoAPI Base CSPs to specify the driver DLL for a hardware accelerator. By design, such a DLL would have access to users' public and private keys. Although only administrators should have permission to add such a DLL, the permissions on the key actually would allow any user who could interactively log onto the machine to do so. By writing a false DLL and installing it, a malicious user could compromise the keys of other users who subsequently used the machine.

The machines primarily at risk would be workstations and terminal servers. Microsoft Windows NT 4.0 Workstation, NT 4.0 Server, NT 4.0 Server, Enterprise Edition, and NT 4.0 Server, Terminal Server Edition are all affected. Windows 2000 is not affected.

A patch is available for Intel x86 machines at and for Compaq Alpha machines at - Isaac Slepner

About the Author

Scott Bekker is editor in chief of Redmond Channel Partner magazine.