DOCUMENT:Q305399 12-JUN-2002 [winnt] TITLE :Malformed Request to RPC Endpoint Mapper can Cause RPC Service t PRODUCT :Microsoft Windows NT PROD/VER::4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a OPER/SYS: KEYWORDS:kbSecurity kbWinNT400PreSP7Fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4, 4.0 SP5, 4.0 SP6a - Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4, 4.0 SP5, 4.0 SP6a - Microsoft Windows NT Workstation versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4, 4.0 SP5, 4.0 SP6a - Microsoft Windows NT Server versions 4.0, 4.0 SP4, 4.0 SP5, 4.0 SP6, Terminal Server Edition ------------------------------------------------------------------------------- SYMPTOMS ======== The RPC (Remote Procedure Call) endpoint mapper allows RPC clients to determine the port number currently assigned to a particular RPC service. Because the endpoint mapper runs within the RPC service itself, exploiting this vulnerability would cause the RPC service itself to fail, with the attendant loss of any RPC-based services the server offers, as well as potential loss of some COM functions. Normal service could be restored by rebooting the system. Standard security recommendations call for port 135 (the port on which the RPC endmapper operates) to be blocked at the firewall. If this were done, the chief threat posed by this vulnerability would be from internal attacks. CAUSE ===== This vulnerability results because the Windows NT 4.0 Remote Procedure Call (RPC) service will fail if the endpoint mapper is sent a request that contains a particular type of malformed data. RESOLUTION ========== A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems that are determined to be at risk of attack. Please evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. Please see the associated Microsoft Security Bulletin (http://www.microsoft.com/technet/security/bulletin/ms01-048.asp) to help make this determination. This fix may receive additional testing at a later time, to further ensure product quality. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. To resolve this problem immediately, download the fix as instructed below or 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/default.aspx?scid=fh;EN-US;CNTACTMS NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal 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: DownloadDownload Q305399i.exe now (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=32503) NOTE: A patch for Windows NT Server 4.0, Terminal Server Edition is forthcoming. Release Date: September 10, 2001 For additional information about how to download Microsoft Support files, click the article number below to view the article in the Microsoft Knowledge Base: Q119591 How to Obtain Microsoft Support Files from Online Services Microsoft used the most current virus detection software available on the date of posting to scan this file for viruses. After it is posted, the file is housed on secure servers that 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 ------------------------------------------------------ 09-Aug-2001 10:56 4.0.1381.7097 701,200 Ole32.dll 09-Aug-2001 10:56 4.0.1381.7097 343,312 Rpcrt4.dll 16-Aug-2001 12:01 4.0.1381.7097 107,280 Rpcss.exe NOTE: Due to file dependencies, this hotfix requires Microsoft Windows NT 4.0 Service Pack 6a (SP6a). STATUS ====== Microsoft has confirmed that this problem could result in some degree of security vulnerability in Windows NT 4.0. MORE INFORMATION ================ For more information on this vulnerability, see the following Microsoft Web site: http://www.microsoft.com/technet/security/bulletin/ms01-048.asp Additional query words: security_patch DoS denial of service ====================================================================== Keywords : kbSecurity kbWinNT400PreSP7Fix Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTW400sp5 kbWinNTW400sp4 kbWinNTW400sp3 kbWinNTW400sp2 kbWinNTW400sp1 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp5 kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp6 kbWinNTS400sp5 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400sp2 kbWinNTS400sp1 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServ400sp4 kbNTTermServ400sp5 kbNTTermServ400sp6 kbNTTermServSearch kbWinNTSEnt400SP6a kbWinNTW400SP6a Version : :4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a 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.