DOCUMENT:Q231457 TITLE :Malformed Request Causes LSA Service to Hang PRODUCT :Windows NT PROD/VER:4.0 OPER/SYS:WINDOWS NT KEYWORD :kbbug4.00 kbfix4.00 ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4 - Microsoft Windows NT Server versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4 - Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4 ------------------------------------------------------------------------------- SYMPTOMS ======== A specially malformed request to the Microsoft Local Security Authority (LSA) service may be used to exploit a security vulnerability on a Windows NT-based computer. A user can abuse this vulnerability to run a program and cause a denial of service attack that may cause the LSA service to stop responding (hang) and require you to restart the computer. CAUSE ===== Windows NT provides the ability to manage user privileges programmatically via the Local Security Authority (LSA) application programming interface (API). This API allows a program to query user names, modify privileges, and change other elements of the security policy, subject to the program's authorizations. Certain API methods have unchecked buffers. If a call is made using a specially malformed argument, the LSA service may stop responding (hang). The vulnerability is a denial of service threat only, and the LSA service can be restored by rebooting the machine. This vulnerability cannot be used by unauthorized program to query or modify user information or privileges. RESOLUTION ========== A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Windows NT 4.0 service pack that contains this fix. To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web: http://support.microsoft.com/support/supportnet/default.asp The English version of this fix should have the following file attributes or later: Date Time Size File name Platform ------------------------------------------------------------- 04/28/99 07:41p 154,896 Lsasrv.dll x86 05/04/99 07:56p 10,000 Lsass.exe x86 04/27/99 07:38p 253,200 Lsasrv.dll Alpha 05/04/99 07:54p 16,144 Lsass.exe Alpha NOTE: This fix can be installed on Windows NT 4.0 Service Pack 4 and Service Pack 5. This hotfix has been posted to the following Internet location as Lsareqi.exe (x86) and Lsareqa.exe (Alpha): ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/ hotfixes-postSP5/LSA3-fix/ NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee. For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base: Q154871 Determining If You Are Eligible for No-Charge Technical Support STATUS ====== Microsoft has confirmed this to be a problem in Windows NT 4.0. MORE INFORMATION ================ For additional security related information about Microsoft products, please visit the Web site at: http://www.microsoft.com/security/ Additional query words: ============================================================================ THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.