RDisk Race Condition

RDisk Race Condition
Originally reported January 21, 2000 by Arne Vidstrom
and updated on February 4, 2000 by Microsoft

Windows NT 4.0 Workstation
  • Windows NT 4.0 Server
  • Windows NT 4.0 Server Enterprise Edition
  • Windows NT 4.0 Terminal Server

    According to Microsoft"s report, "The RDISK utility is used to create an Emergency Repair Disk (ERD) in order to record machine state information as a contingency against system failure. During execution, RDISK creates a temporary file containing an enumeration of the registry. The ACLs on the file allow global read permission, and as a result, a malicious user who knew that the administrator was running RDISK could open the file and read the registry enumeration information as it was being created. RDISK erases the file upon successful completion, so under normal conditions there would be no lasting vulnerability.

    By default, the file is not shared and therefore could not be read by other network users."

    The utility is provided as part of all versions of Windows NT 4.0 and the vulnerability exists on each NT 4.0 platform.


    Microsoft has released a FAQ, Support Online articles Q156328 and Q249108, a patch for Terminal Server and patches for NT 4.0 Wkstn,  Server, and Enterprise Edition on Intel and Alpha platforms.

    Discovered by
    Arne Vidstrom

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