DOCUMENT:Q230677 16-MAY-2002 [winnt] TITLE :Malformed Phonebook Entry Security Vulnerability in RAS Client PRODUCT :Microsoft Windows NT PROD/VER:winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4 OPER/SYS: KEYWORDS:kbWinNT4sp6fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server version 4.0, Terminal Server Edition - 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 ======== Microsoft Remote Access Service (RAS) client software may allow a user with the proper permissions to mount a denial-of-service attack or elevate his or her privileges on a RAS client computer. CAUSE ===== This behavior occurs because the RAS client component that processes phonebook entries has an unchecked buffer. As a result, a specially malformed RAS phonebook entry can cause the RAS client to crash. In very specific conditions, it can cause arbitrary code to run on the client computer. Because the RAS client operates in the security context of the local computer, the arbitrary code also runs in this context. This cannot occur accidentally. RESOLUTION ========== Windows NT Server or Workstation 4.0 ------------------------------------ To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to: - http://www.microsoft.com/Windows/ServicePacks/ -or- - Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack For information on obtaining the individual software update, contact Microsoft Product Support Services. 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/default.aspx?scid=fh;EN-US;CNTACTMS Windows NT Server 4.0, Terminal Server Edition ---------------------------------------------- To resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, please see the following article in the Microsoft Knowledge Base: Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack STATUS ====== Microsoft has confirmed this to be a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows NT Server version 4.0, Terminal Server Edition Service Pack 6. MORE INFORMATION ================ This vulnerability affects only computers running the RAS client software; it does not affect RAS servers. A user must have permission to add or modify phonebook entries to initiate an attack. Permissions can be set using the phonebook's access control list (ACL). Computers at risk because of this vulnerability are workstations that are configured to dial other computers as servers, including Microsoft Windows NT 4.0, Terminal Server Edition, but are not typically configured to act as RAS clients. This vulnerability affects only local computers; a user cannot directly attack remote computers. For additional security-related information about Microsoft products, please visit the following Microsoft Web site: http://www.microsoft.com/security/ Additional query words: ====================================================================== Keywords : kbWinNT4sp6fix Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTW400sp4 kbWinNTW400sp3 kbWinNTW400sp2 kbWinNTW400sp1 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400sp2 kbWinNTS400sp1 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch Version : winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4 Hardware : ALPHA x86 Issue type : kbbug Solution Type : kbfix ============================================================================= 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. Copyright Microsoft Corporation 2002.