Vulnerability Note VU#818496

Microsoft Windows 2000 Workstation in mixed-mode domain may ignore domain account lockout restriction due to flaw in NTLM authentication

Original Release date: 01 May 2001 | Last revised: 25 Jun 2001


A flaw in certain configurations of Windows 2000 can allow an intruder to make an unlimited number of guesses to attempt to determine a password, despite policies intended to limit the number of guesses.


Domain administrators can set policies governing certain aspects of behavior within a domain. One of the policies that can be set is the number of failed password attempts before the account will be locked out. This is intended to prevent an intruder from attempting to guess a password through brute force. Under some circumstances, described in detail in Microsoft Security Bulletin MS-089, the policy can be circumvented, allowing an intruder to make repeated unlimited attempts to guess a password. The policy would be enforced relative to attempts to authenticate to the domain, but not relative to cached credentials.


An intruder can attempt to guess (possibly in an automated fashion) passwords on a Windows 2000 machine.


Apply the patches and workarounds described in

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
MicrosoftAffected-30 Apr 2001
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



Our thanks to Microsoft for the information contained in their advisory, and to Finch Brett, who reported the information to Microsoft.

This document was written by Shawn V. Hernan.

Other Information

  • CVE IDs: Unknown
  • Date Public: 21 Nov 2000
  • Date First Published: 01 May 2001
  • Date Last Updated: 25 Jun 2001
  • Severity Metric: 3.15
  • Document Revision: 9


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