__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft Vulnerability in POSIX Could Allow Code Execution [Microsoft Security Bulletin MS04-020] July 14, 2004 17:00 GMT Number O-181 [REVISED 10 Aug 2004] ______________________________________________________________________________ PROBLEM: An unchecked buffer vulnerability exists in the Portable Operating System Interface for UNIX (POSIX) operating system component (subsystem). POSIX provides support for nonnative applications by emulating the environment in which it was designed to be processed. PLATFORM: Microsoft Windows NT Workstation 4.0 Service Pack 6a Microsoft Windows NT Server 4.0 Service Pack 6a Microsoft Windows NT Server 4.0 Terminal Server Edition Service Pack Microsoft Windows 2000 Service Pack 2 Microsoft Windows 2000 Service Pack 3 Microsoft Windows 2000 Service Pack 4 Microsoft INTERIX 2.2 DAMAGE: An attacker who logs on to a local system that has POSIX subsystem enabled may take complete control of an affected system, including installing programs; viewing, changing or deleting data; or creating new accounts that have full privileges. SOLUTION: Install the security update. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. A local attacker could gain root ASSESSMENT: privileges. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/o-181.shtml ORIGINAL BULLETIN: http://www.microsoft.com/technet/security/bulletin/ ms04-020.mspx CVE/CAN: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name= CAN-2004-0210 ______________________________________________________________________________ REVISION HISTORY: 08/10/04 - added INTERIX 2.2 to Affected Software section of Microsoft Security Bulletin MS04-020. [***** Start Microsoft Security Bulletin MS04-020 *****] Microsoft Security Bulletin MS04-020 Vulnerability in POSIX Could Allow Code Execution (841872) Issued: July 13, 2004 Updated: August 10, 2004 Version: 2.0 Summary Who should read this document: Customers who use Microsoftฎ Windowsฎ 2000 or Windows NT 4.0 Impact of Vulnerability: Local Elevation of Privilege Maximum Severity Rating: Important Recommendation: Customers should install the update at the earliest opportunity. Security Update Replacement: None Caveats: None Tested Software and Security Update Download Locations: Affected Software: • Microsoft INTERIXฎ 2.2 – Download the update • Microsoft Windows NTฎ Workstation 4.0 Service Pack 6a – Download the update • Microsoft Windows NT Server 4.0 Service Pack 6a – Download the update • Microsoft Windows NT Server 4.0 Terminal Server Edition Service Pack 6 – Download the update • Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, Microsoft Windows 2000 Service Pack 4 – Download the update Non-Affected Software: • Microsoft Windows XP and Microsoft Windows XP Service Pack 1 • Microsoft Windows XP 64-Bit Edition Service Pack 1 • Microsoft Windows XP 64-Bit Edition Version 2003 • Microsoft Windows Server™ 2003 • Microsoft Windows Server 2003 64-Bit Edition • Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (Me) The software in this list has been tested to determine if the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support lifecycle for your product and version, visit the following Microsoft Support Lifecycle Web site. Top of section General Information Executive Summary Executive Summary: This update resolves a newly-discovered, privately reported vulnerability. A privilege elevation vulnerability exists in the POSIX operating system component (subsystem). The vulnerability is documented in the Vulnerability Details section of this bulletin. An attacker who successfully exploited this vulnerability could take complete control of an affected system, including installing programs; viewing, changing, or deleting data; or creating new accounts that have full privileges. We recommend that customers install the update at the earliest opportunity. Severity Ratings and Vulnerability Identifiers: Vulnerability Identifiers: POSIX Vulnerability - CAN-2004-0210 Impact of Vulnerability: Privilege Elevation Windows NT 4.0: Important Windows 2000: Important This assessment is based on the types of systems that are affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them. Top of section Frequently asked questions (FAQ) related to this security update Top of section Vulnerability Details POSIX Vulnerability - CAN-2004-0210 A privilege elevation vulnerability exists in the POSIX subsystem. This vulnerability could allow a logged on user to take complete control of the system. Mitigating Factors for POSIX Vulnerability - CAN-2004-0210: • An attacker must have valid logon credentials and be able to logon locally to exploit this vulnerability. The vulnerability could not be exploited remotely or by anonymous users. • Windows XP and Windows Server 2003 are not affected by this vulnerability. Top of section Workarounds for POSIX Vulnerability - CAN-2004-0210: Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified below. • Disable the POSIX subsystem through the registry This workaround is fully documented in Microsoft Knowledge Base Article 101270. This article is summarized in the following paragraphs. The following steps demonstrate how to disable the POSIX subsystem. Note Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note We recommend backing up the registry before you edit it. 1. Click Start, click Run, type "regedt32" (without the quotation marks), and then click OK. 2. In Registry Editor, locate the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Subsystems\Posix 3. Click the POSIX data value, click Edit, and then click Delete. 4. Click OK to confirm the delete, and then restart the system. Note To enable the POSIX subsystem, re-create the registry key. The name if the registry key is Posix, the type of registry key is REG_EXPAND_SZ, and the registry key value is %SystemRoot%\system32\psxss.exe. After you have done this, restart the system. Impact of Workaround: POSIX programs are disabled until the POSIX subsystem is enabled. Top of section FAQ for POSIX Vulnerability - CAN-2004-0210: Top of section Top of section Top of section Security Update Information Installation Platforms and Prerequisites: For information about the specific security update for your platform, click the appropriate link: Windows 2000 (all versions) Prerequisites For Windows 2000, this security update requires Service Pack 2 (SP2), Service Pack 3 (SP3), or Service Pack 4 (SP4). The software that is listed has been tested to determine if the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support lifecycle for your product and version, visit the Microsoft Support Lifecycle Web site. For more information about how to obtain the latest service pack, see Microsoft Knowledge Base Article 260910. Inclusion in Future Service Packs: The update for this issue will be included in Windows 2000 Service Pack 5. Installation Information This security update supports the following setup switches: /help Displays the command line options Setup Modes /quiet Quiet mode (no user interaction or display) /passive Unattended mode (progress bar only) /uninstall Uninstalls the package Restart Options /norestart Do not restart when installation is complete /forcerestart Restart after installation Special Options /l Lists installed Windows hotfixes or update packages /o Overwrite OEM files without prompting /n Do not backup files needed for uninstall /f Force other programs to close when the computer shuts down /extract Extracts files without starting setup Note You can combine these switches into one command. For backward compatibility, the security update also supports the setup switches that the previous version of the setup utility uses. For more information about the supported installation switches, see Microsoft Knowledge Base Article 262841. Deployment Information To install the security update without any user intervention, use the following command at a command prompt for Windows 2000 Service Pack 2, Windows 2000 Service Pack 3, and Windows 2000 Service Pack 4: Windows2000-kb841872-x86-enu /passive /quiet To install the security update without forcing the system to restart, use the following command at a command prompt for Windows 2000 Service Pack 2, Windows 2000 Service Pack 3, and Windows 2000 Service Pack 4: Windows2000-kb841872-x86-enu /norestart For more information about how to deploy this security update with Software Update Services, visit the Software Update Services Web site. Restart Requirement In some cases, this update does not require a restart. The installer stops the required services, applies the update, and then restarts the services. However, if the required services cannot be stopped for any reason or if required files are in use, this update will require a restart. If this occurs, a message appears that advises you to restart. Removal Information To remove this security update, use the Add or Remove Programs tool in Control Panel. System administrators can also use the Spuninst.exe utility to remove this security update. The Spuninst.exe utility is located in the %Windir%\ $NTUninstallKB841872$\Spuninst folder. The Spuninst.exe utility supports the following setup switches: /?: Show the list of installation switches. /u: Use unattended mode. /f: Force other programs to quit when the computer shuts down. /z: Do not restart when the installation is complete. /q: Use Quiet mode (no user interaction). File Information The English version of this update has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. Note Date, time, file name, or size information could change during installation. Refer to the Verifying Update Installation section for details on verifying an installation. Windows 2000 Service Pack 2, Windows 2000 Service Pack 3, and Windows 2000 Service Pack 4: Date Time Version Size File name ------------------------------------------------------ 16-May-2004 19:32 5.0.2195.6929 90,384 Psxss.exe Verifying Update Installation • Microsoft Baseline Security Analyzer To verify that a security update is installed on an affected system, you may be able to use the Microsoft Baseline Security Analyzer (MBSA) tool. This tool allows administrators to scan local and remote systems for missing security updates and for common security misconfigurations. For more information about MBSA, visit the Microsoft Baseline Security Analyzer Web site. • File Version Verification Note Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps. 1. Click Start, and then click Search. 2. In the Search Results pane, click All files and folders under Search Companion. 3. In the All or part of the file name box, type a file name from the appropriate file information table, and then click Search. 4. In the list of files, right-click a file name from the appropriate file information table, and then click Properties. Note Depending on the version of the operating system or programs installed, some of the files that are listed in the file information table may not be installed. 5. On the Version tab, determine the version of the file that is installed on your computer by comparing it to the version that is documented in the appropriate file information table. Note Attributes other than file version may change during installation. Comparing other file attributes to the information in the file information table is not a supported method of verifying the update installation. Also, in certain cases, files may be renamed during installation. If the file or version information is not present, use one of the other available methods to verify update installation. • Registry Key Verification You may also be able to verify the files that this security update has installed by reviewing the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows 2000\SP5\KB841872\Filelist Note This registry key may not contain a complete list of installed files. Also, this registry key may not be created correctly when an administrator or an OEM integrates or slipstreams the 841872 security update into the Windows installation source files. Top of section Windows NT 4.0 (all versions) Prerequisites This security update requires Windows NT Workstation 4.0 Service Pack 6a (SP6a), Windows NT Server 4.0 Service Pack 6a (SP6a), or Windows NT Server 4.0 Terminal Server Edition Service Pack 6 (SP6). The software that is listed has been tested to determine if the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support lifecycle for your product and version, visit the following Microsoft Support Lifecycle Web site. For more information about obtaining the latest service pack, see Microsoft Knowledge Base Article 152734. Installation Information This security update supports the following setup switches: /y: Perform removal (only with /m or /q ) /f: Force programs to quit during the shutdown process /n: Do not create an Uninstall folder /z: Do not restart when the update completes /q: Use Quiet or Unattended mode with no user interface (this switch is a superset of /m ) /m: Use Unattended mode with a user interface /l: List the installed hotfixes /x: Extract the files without running Setup Note You can combine these switches into one command. For more information about the supported installation switches, see Microsoft Knowledge Base Article 262841. Deployment Information To install the security update without any user intervention, use the following command at a command prompt for Windows NT Server 4.0: Windowsnt4server-kb841872-x86-enu /q For Windows NT Server 4.0 Terminal Server Edition: Windowsnt4terminalserver-kb841872-x86-enu /q For Windows NT Workstation 4.0: Windowsnt4workstation-kb841872-x86-enu /q To install the security update without forcing the system to restart, use the following command at a command prompt for Windows NT Server 4.0: Windowsnt4server-kb841872-x86-enu /z For Windows NT Server 4.0 Terminal Server Edition: Windowsnt4terminalserver-kb841872-x86-enu /z For Windows NT Workstation 4.0: Windowsnt4workstation-kb841872-x86-enu /z For more information about how to deploy this security update with Software Update Services, visit the Software Update Services Web site. Restart Requirement In some cases, this update does not require a restart. The installer stops the needed services, applies the update, and then restarts the services. However, if the required services cannot be stopped for any reason or if required files are in use, this update will require a restart. If this occurs, a message appears that advises you to restart. Removal Information To remove this security update, use the Add/Remove Programs tool in Control Panel. System administrators can also use the Hotfix.exe utility to remove this security update. The Hotfix.exe utility is located in the %Windir%\ $NTUninstallKB841872$ folder. The Hotfix.exe utility supports the following setup switches: /y: Perform removal (only with the /m or /q switch) /f: Force programs to quit during the shutdown process /n: Do not create an Uninstall folder /z: Do not restart when the installation is complete /q: Use Quiet or Unattended mode with no user interface (this switch is a superset of the /m switch) /m: Use Unattended mode with a user interface /l: List the installed hotfixes File Information The English version of this update has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. Note Date, time, filename, or size information could change during installation. Refer to the Verifying Update Installation section for details on verifying an installation. Windows NT Workstation 4.0 and Windows NT Server 4.0: Date Time Version Size File name ------------------------------------------------------ 20-May-2004 15:04 4.0.1381.7269 93,968 Psxss.exe Windows NT Server 4.0 Terminal Server Edition: Date Time Version Size File name ------------------------------------------------------- 21-May-2004 13:31 4.0.1381.33567 94,480 Psxss.exe Verifying Update Installation • Microsoft Baseline Security Analyzer To verify that a security update is installed on an affected system, you may be able to use the Microsoft Baseline Security Analyzer (MBSA) tool. This tool allows administrators to scan local and remote systems for missing security updates and for common security misconfigurations. For more information about MBSA, visit the Microsoft Baseline Security Analyzer Web site. • File Version Verification Note Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps. 1. Click Start, and then click Search. 2. In the Search Results pane, click All files and folders under Search Companion. 3. In the All or part of the file name box, type a file name from the appropriate file information table, and then click Search. 4. In the list of files, right-click a file name from the appropriate file information table, and then click Properties. Note Depending on the version of the operating system or programs installed, some of the files that are listed in the file information table may not be installed. 5. On the Version tab, determine the version of the file that is installed on your computer by comparing it to the version that is documented in the appropriate file information table. Note Attributes other than file version may change during installation. Comparing other file attributes to the information in the file information table is not a supported method of verifying the update installation. Also, in certain cases, files may be renamed during installation. If the file or version information is not present, use one of the other available methods to verify update installation. • Registry Key Verification You may also be able to verify the files that this security update has installed by reviewing the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Hotfix\ KB841872\File 1 Note This registry key may not contain a complete list of installed files. Also, this registry key may not be created correctly when an administrator or an OEM integrates or slipstreams the 841872 security update into the Windows installation source files. Top of section Top of section Acknowledgments Microsoft thanks the following for working with us to help protect customers: • Rafal Wojtczuk working with McAfee for reporting the POSIX Vulnerability (CAN-2004-0210). Obtaining Other Security Updates: Updates for other security issues are available from the following locations: • Security updates are available from the Microsoft Download Center: You can find them most easily by doing a keyword search for "security_patch". • Updates for consumer platforms are available from the Windows Update Web site. Support: • Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates. • International customers can receive support from their local Microsoft subsidiaries. There is no charge for support that is associated with security updates. For more information about how to contact Microsoft for support issues, visit the International Support Web site. Security Resources: • The Microsoft TechNet Security Web site provides additional information about security in Microsoft products. • Microsoft Software Update Services • Microsoft Baseline Security Analyzer (MBSA) • Windows Update • Windows Update Catalog: For more information about the Windows Update Catalog, see Microsoft Knowledge Base Article 323166. • Office Update Software Update Services: By using Microsoft Software Update Services (SUS), administrators can quickly and reliably deploy the latest critical updates and security updates to Windows 2000 and Windows Server 2003-based servers, and to desktop systems that are running Windows 2000 Professional or Windows XP Professional. For more information about how to deploy this security update with Software Update Services, visit the Software Update Services Web site. Systems Management Server: Microsoft Systems Management Server (SMS) delivers a highly-configurable enterprise solution for managing updates. By using SMS, administrators can identify Windows-based systems that require security updates and to perform controlled deployment of these updates throughout the enterprise with minimal disruption to end users. For more information about how administrators can use SMS 2003 to deploy security updates, see the SMS 2003 Security Patch Management Web site. SMS 2.0 users can also use Software Updates Service Feature Pack to help deploy security updates. For information about SMS, visit the SMS Web site. Note SMS uses the Microsoft Baseline Security Analyzer and the Microsoft Office Detection Tool to provide broad support for security bulletin update detection and deployment. Some software updates may not be detected by these tools. Administrators can use the inventory capabilities of the SMS in these cases to target updates to specific systems. For more information about this procedure, see the following Web site. Some security updates require administrative rights following a restart of the system. Administrators can use the Elevated Rights Deployment Tool (available in the SMS 2003 Administration Feature Pack and in the SMS 2.0 Administration Feature Pack) to install these updates. Disclaimer: 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. Revisions: • V1.0 (July 13, 2004): Bulletin published • V2.0 (August 10, 2004): Updated to reflect an additional affected product - Microsoft INTERIX 2.2 [***** End Microsoft Security Bulletin MS04-020 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft Corporation for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. 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