Microsoft KB Archive/300905

= MS01-031: Handle Leak in Telnet Service Causes a Denial-of-Service Vulnerability =

Article ID: 300905

Article Last Modified on 1/31/2007

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APPLIES TO


 * Microsoft Windows 2000 Service Pack 1
 * Microsoft Windows 2000 Service Pack 2
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Service Pack 2
 * Microsoft Windows 2000 Service Pack 1

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This article was previously published under Q300905



SYMPTOMS
A denial-of-service vulnerability exists in the Windows 2000 Telnet service because of a handle leak when a Telnet session is terminated in a certain way. By repeatedly starting sessions and then terminating them, an attacker could deplete the supply of handles on the server to the point where it could no longer perform useful work.

Mitigating Factors

 * It would not be necessary to reboot the server to recover from this vulnerability. At worst, the Telnet service would need to be restarted.
 * This vulnerability cannot be used to gain additional privileges on the computer; it is a denial-of-service vulnerability only.



RESOLUTION
To resolve this problem, either obtain the hotfix referenced in this section or the 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:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

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:

Download Q299553_w2k_sp3_x86_en.exe now

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



STATUS
Microsoft has confirmed that this problem may cause a degree of security vulnerability in Microsoft Windows 2000.



MORE INFORMATION
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:

http://www.microsoft.com/technet/security/bulletin/MS01-031.mspx

For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the article number below to view the article in the Microsoft Knowledge Base:

249149 Installing Microsoft Windows 2000 and Windows 2000 Hotfixes

Additional query words: security_patch DoS kbWin2000srp1

Keywords: kbbug kbfix kbwin2000presp3fix kbgraphxlinkcritical kbsecvulnerability kbqfe kbsecurity kbsecdos kbsechack KB300905

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