MS01-031: Telnet Service Allows Logging On to Domain Guest Account

This article was previously published under Q300901
This article has been archived. It is offered "as is" and will no longer be updated.
An information-disclosure vulnerability exists in the Windows 2000 Telnet service that can make it easier for an attacker to exploit an incorrectly configured network. It would not give an attacker a way to do anything that the attacker could not already do. In the worst case, the vulnerability could assist an attacker in gaining access to a domain account.

This vulnerability has a number of significant restrictions:
  • The attacker would need to know the correct password for the account. The most likely account to be affected--the Guest account--is disabled by default.
  • The vulnerability could only be exploited if the system administrator had made the Telnet server a domain member.
If a user ID is specified in a particular way when a user logs on to an affected Telnet server, the system automatically searches all trusted domains for a user ID that matches it. If the user ID is found and the correct password is provided, the system will allow the user to log on to the account normally.
To resolve this problem, either obtain the hotfix referenced in this section or Windows 2000 Security Rollup Package 1 (SRP1). For additional information about SRP1, click the article number below to view the article in the Microsoft Knowledge Base:
311401 Windows 2000 Security Rollup Package 1 (SRP1), January 2002
A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that you determine are at risk of attack. Evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. See the associated Microsoft Security Bulletin to help determine the degree of risk. This fix may receive additional testing. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. Otherwise, wait for the next Windows 2000 service pack that contains this fix.

To resolve this problem immediately, download the fix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The following file is available for download from the Microsoft Download Center:
Release Date: June 7, 2001

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

The English version of this fix should have the following file attributes or later:
   Date        Time    Version      Size     File name   -----------------------------------------------------   05/24/2001  04:14p  5.0.33667.1  186,128  Tlntsvr.exe				

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Microsoft Windows 2000.
For additional information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the article number below to view the article in the Microsoft Knowledge Base:
265173 The Datacenter Program and Windows 2000 Datacenter Server Product
For additional information about how to install multiple hotfixes with only one reboot, click the article number below to view the article in the Microsoft Knowledge Base:
296861 Use QChain.exe to Install Multiple Hotfixes with One Reboot
For additional information about what is fixed by this patch, click the article number below to view the article in the Microsoft Knowledge Base:
300855 Windows 2000 Telnet Security Rollup
For more information about this vulnerability, see the following Microsoft Web site:This vulnerability has exactly the same cause, scope, and effect as a vulnerability that affects FTP and is discussed in the following Microsoft Security Bulletin:
security_patch kbWin2000srp1

Article ID: 300901 - Last Review: 02/27/2014 21:08:52 - Revision: 5.3

Microsoft Windows 2000 Server SP1, Microsoft Windows 2000 Server SP2, Microsoft Windows 2000 Advanced Server SP1, Microsoft Windows 2000 Advanced Server SP2, Microsoft Windows 2000 Professional SP2, Microsoft Windows 2000 Professional SP1

  • kbnosurvey kbarchive kbbug kbfix kbgraphxlinkcritical kbqfe kbsecbulletin kbsechack kbsecurity kbsecvulnerability kbwin2000presp3fix KB300901
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