DOCUMENT:Q218473 11-JUN-2002 [winnt] TITLE :Restricting Changes to Base System Objects PRODUCT :Microsoft Windows NT PROD/VER:winnt:3.5,3.51,4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4 OPER/SYS: KEYWORDS:kbWinNT400sp5fix _IK ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4 - Microsoft Windows NT Server versions 3.5, 3.51, 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 - Microsoft Windows NT Server version 4.0, Terminal Server Edition ------------------------------------------------------------------------------- IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base: Q256986 Description of the Microsoft Windows Registry SYMPTOMS ======== If a non-administrative level user logs on interactively to your computer, it may be possible for the user to gain local administrative privileges. A user may load a non-Microsoft dynamic-link library (DLL) into memory having the same name as a core operating system DLL and then programmatically change the entry in the KnownDLLs list to point to the malicious copy. Programs then requesting the system DLL will instead be directed to the malicious copy. When called by a program with sufficiently high security privileges, it may be possible to bypass typical security related activities such as adding a user to the Local Administrators group. A remote user may also submit an arbitrary program to run on your computer to exploit this vulnerability. CAUSE ===== In Windows NT, core operating system DLLs are kept in virtual memory and shared between programs. This prevents redundant copies of the DLL in memory, and improves memory usage and system performance. When a program calls a function provided by one of these DLLs, the operating system refers to a data structure called the KnownDLLs list to determine the location of the DLL in virtual memory. The Windows NT security architecture protects in-memory DLLs against modification, but by default it allows all users to read/write access to the KnownDLLs list. This vulnerability is only local to the computer where a malicious user is logged on interactively. For example, a workstation user could exploit this vulnerability to become a local administrator, but cannot use it directly to become a domain administrator. This restricts the impact of this issue as non-administrative users are not granted the ability to interactively log on to servers (following recommended Microsoft security practices). RESOLUTION ========== NOTE: You should apply this fix to all systems that allow non-privileged users to log in to them. Windows NT 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 This hotfix has been posted to the following Internet location as Smssfixi.exe (x86) and Smssfixa.exe (Alpha): ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/hotfixes-postSP4/Smss-fix/ 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 This hotfix has been posted to the following Internet location as Smssfixi.exe (x86) and Smssfixa.exe (Alpha): ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40TSE/hotfixes-postSP3/Smss-fix/ Windows NT 3.51 --------------- 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 experiencing this specific problem. To resolve this problem, 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 English version of this fix should have the following file attributes or later: Date Time Size File name Platform ------------------------------------------------------------- 03/24/99 09:56p 37,328 Smss.exe (x86) 03/24/99 09:59p 54,544 Smss.exe (Alpha) WORKAROUND ========== WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk. To work around this issue, enable stronger protection on system base objects such as the KnownDLLs list by doing the following: 1. Click Start, click Run, type "regedt32" (without the quotation marks), and then click OK. 2. On the Windows menu, click "HKEY_LOCAL_ MACHINE on Local Machine". 3. Double-click the \System\CurrentControlSet\Control\Session Manager folder. 4. On the Edit menu, click Add Value, type "ProtectionMode" (without the quotation marks), click REG_DWORD in the Data Type box, and then click OK. 5. Type "1" (without the quotation marks) in the Data box, and then click OK. 6. Quit Registry Editor, and then restart the computer. STATUS ====== Microsoft has confirmed this problem could result in some degree of security vulnerability in the Microsoft products listed at the beginning of this article. This problem was first corrected in Windows NT Server 4.0, Terminal Server Edition Service Pack 4. This problem was first corrected in Windows NT version 4.0 Service Pack 5. MORE INFORMATION ================ For additional security related information about Microsoft products, please visit the Web site at: http://www.microsoft.com/security/ Additional query words: ====================================================================== Keywords : kbWinNT400sp5fix _IK Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351search kbWinNT350search kbWinNT400search kbWinNTW350 kbWinNTW350search kbWinNTW351search kbWinNTW351 kbWinNTW400sp4 kbWinNTW400sp3 kbWinNTW400sp2 kbWinNTW400sp1 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400sp2 kbWinNTS400sp1 kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS350 kbNTTermServ400 kbNTTermServSearch kbWinNTS351search kbWinNTS350search Version : winnt:3.5,3.51,4.0,4.0 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. 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