O-178: Vulnerability in Task Scheduler Could Allow Code Execution Privacy and Legal Notice

CIAC INFORMATION BULLETIN

O-178: Vulnerability in Task Scheduler Could Allow Code Execution

[Microsoft Security Bulletin MS04-022]

July 13, 2004 22:00 GMT
[REVISED 20 Jul 2004]

PROBLEM: A vulnerability exists in the Windows Task Scheduler because of an unchecked buffer. Task Scheduler is used to schedule commands, programs, or scripts to run at specific times.
PLATFORM: Microsoft Windows 2000 Service Pack 2,
Microsoft Windows 2000 Service Pack 3,
Microsoft Windows 2000 Service Pack 4,
Microsoft Windows XP and
Microsoft Windows XP Service Pack 1,
Microsoft Windows XP 64-Bit Edition Service Pack 1
Internet Explorer 6 Service Pack 1 when installed on Windows NT 4.0 SP6a (Workstation, Server, or Terminal Server Edition)
Caveat: Windows NT Workstation 4.0, Windows NT Server 4.0 and Windows NT 4.0 Terminal Server Edition are not affected by default. However if you have installed Internet Explorer 6.0 Service Pack 1 you will have the vulnerable component on your system.
DAMAGE: If a user is logged on with administrative privileges, 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 with full privileges. However, user interaction is required to exploit this vulnerability. Users whose accounts are configured to have fewer privileges on the system would be at less risk than users who operate with administrative privileges.
SOLUTION: Apply security updates.

VULNERABILITY
ASSESSMENT:
The risk is HIGH. A remote attacker may gain root level privileges.

LINKS:  
  CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/o-178.shtml
  ORIGINAL BULLETIN: http://www.microsoft.com/technet/security/bulletin/ms04-022.mspx
  ADDITIONAL LINK: Symantec Security Response #10708
http://securityresponse.symantec.com/avcenter/security/Content/10708.html
  CVE/CAN: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0212

REVISION HISTORY:
7/20/04 - updated the Workaround section in the body of Microsoft's bulletin. 
   
  
[***** Start Microsoft Security Bulletin MS04-022 *****]

Microsoft Security Bulletin MS04-022

Vulnerability in Task Scheduler Could Allow Code Execution (841873)

Issued: July 13, 2004
Updated: July 19, 2004
Version: 1.1

Summary

Who should read this document: Customers who use Microsoftฎ Windowsฎ

Impact of Vulnerability: Remote Code Execution

Maximum Severity Rating: Critical

Recommendation: Customers should apply the update immediately.

Security Update Replacement: None

Caveats: 
Subsequent to the release of this bulletin, an additional work around was 
discovered which can prevent the possibility of an attack. For details, 
please view the "Workarounds" section of the bulletin under "Vulnerability 
Details".

Windows NT Workstation 4.0, Windows NT Server 4.0 and Windows NT 4.0 
Terminal Server Edition are not affected by default. However if you have 
installed Internet Explorer 6.0 Service Pack 1 you will have the vulnerable 
component on your system.


Tested Software and Security Update Download Locations:

Affected Software: 

• Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, 
  Microsoft Windows 2000 Service Pack 4 – Download the update
 
• Microsoft Windows XP and Microsoft Windows XP Service Pack 1 – Download the 
  update
 
• Microsoft Windows XP 64-Bit Edition Service Pack 1 – Download the update
 

Non-Affected Software:

• Microsoft Windows Server™ 2003
 
• Microsoft Windows Server 2003 64-Bit Edition
 
• Microsoft Windows XP 64-Bit Edition Version 2003
 
• Microsoft Windows NTฎ 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 6
 
• Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft 
  Windows Millennium Edition (Me)
 

Tested Microsoft Windows Components:

Affected Components:

• Internet Explorer 6 Service Pack 1 when installed on Windows NT 4.0 SP6a 
  (Workstation, Server, or Terminal Server Edition) - Download the update
 

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.

General Information

Executive Summary:

This update resolves a newly-discovered, privately reported vulnerability. 
A remote code execution vulnerability exists in the Task Scheduler because 
of an unchecked buffer. The vulnerability is documented in the Vulnerability 
Details section of this bulletin.

If a user is logged on with administrative privileges, 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 with full privileges. However, 
user interaction is required to exploit this vulnerability. Users whose 
accounts are configured to have fewer privileges on the system would be 
at less risk than users who operate with administrative privileges.

We recommend that customers apply the update immediately.

Severity Ratings and Vulnerability Identifiers:

Vulnerability Identifiers Impact of Vulnerability Internet Explorer 6 Windows 
2000 Windows XP 

Task Scheduler Vulnerability - CAN-2004-0212
 Remote Code Execution
 Critical
 Critical
 Critical
 

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 

How does the extended support for Windows 98, Windows 98 Second Edition, 
and Windows Millennium Edition affect the release of security updates for 
these operating systems?

Microsoft will only release security updates for critical security issues. 
Non-critical security issues are not offered during this support period. 
For more information about the Microsoft Support Lifecycle policies for these 
operating systems, visit the following Web site.

For more information about severity ratings, visit the following Web site.

Are Windows 98, Windows 98 Second Edition, or Windows Millennium Edition 
critically affected by any of the vulnerabilities that are addressed in 
this security bulletin?

No. None of these vulnerabilities are critical in severity on Windows 98, 
on Windows 98 Second Edition, or on Windows Millennium Edition, even with 
Internet Explorer 6 SP1 installed.

Is Windows NT 4.0 Service Pack 6a affected by the vulnerability that is 
addressed in this security bulletin?

By default, this operating system does not natively provide a version of 
the vulnerable component and is not affected. However, the vulnerable component 
is installed on this operating system when you install Internet Explorer 6. 
If you use this version of Internet Explorer on this operating system, you 
should install the provided security update for Internet Explorer 6.

I'm still using Microsoft Windows NT 4.0 Workstation Service Pack 6a or Windows 
2000 Service Pack 2, but extended security update support ended on June 30, 2004. 
However, this bulletin has a security update for these operating system versions. 
Why is that?

Windows NT 4.0 Workstation Service Pack 6a and Windows 2000 Service Pack 2 have 
reached the end of their life cycles as previously documented, and Microsoft 
extended this support to June 30, 2004. However, the end-of-life for the extended 
support period occurred very recently. In this case, the majority of the steps 
that are required to address this vulnerability were completed before June 30, 
2004. Therefore, we have decided to release security updates for these operating 
system versions as part of this security bulletin. We do not anticipate doing 
this for future vulnerabilities affecting these operating system versions, but 
we reserve the right to produce updates and to make these updates available 
when necessary. 

It should be a priority for customers who have these operating system versions 
to migrate to supported versions to prevent potential exposure to future 
vulnerabilities. For more information about the Windows Product Life Cycle, 
visit the following Microsoft Support Lifecycle Web site. For more information 
about the extended security update support period for these operating system 
versions, visit the following Microsoft Product Support Services Web site. 

Customers who require additional support for Windows NT Workstation 4.0 SP6a 
must contact their Microsoft account team representative, their Technical 
Account Manager, or the appropriate Microsoft partner representative for custom 
support options. Customers without an Alliance, Premier, or Authorized Contract 
can contact their local Microsoft sales office. For contact information, visit 
the Microsoft Worldwide Information Web site, select the country, and then 
click Go to see a list of phone numbers. When you call, ask to speak with the 
local Premier Support sales manager. 

For more information, see the Windows Operating System FAQ.

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine if this 
update is required?

MBSA will determine if this update is required for Windows 2000 (all versions) 
and Windows XP (all versions). MBSA does not currently support the full 
detection of this update for the Windows NT 4.0 product (all versions). For 
more information about MBSA, visit the MBSA Web site.

Note After April 20, 2004, the Mssecure.xml file that is used by MBSA 1.1.1 
and earlier versions is no longer being updated with new security bulletin 
data. Therefore, scans that are performed after that date with MBSA 1.1.1 or 
earlier will be incomplete. All users should upgrade to MBSA 1.2 because it 
provides more accurate security update detection and supports additional 
products. Users can download MBSA 1.2 from the MBSA Web site. For more 
information about MBSA support, visit the following Microsoft Baseline Security 
Analyzer 1.2 Q&A Web site.

Can I use Systems Management Server (SMS) to determine if this update is required?

SMS uses MBSA for detection. SMS can help detect and deploy this security 
update for Windows 2000 (all versions) and Windows XP (all versions). This 
update is not detected by MBSA for the Windows NT 4.0 product (all versions). 
However, the file and registry key information that is available in this 
bulletin can be used to write specific file and registry key collection queries 
in SMS to detect vulnerable computers. For information about how to deploy 
updates not supported by MBSA with SMS, please review Knowledge Base article 
867832. For information about SMS, visit the SMS Web site.

Top of section
 Vulnerability Details 


 Task Scheduler Vulnerability - CAN-2004-0212
:  

A remote code execution vulnerability exists in the Task Scheduler because 
of the way that it handles application name validation. There are many ways 
that a system could be vulnerable to this attack. An attacker who successfully 
exploited this vulnerability could take complete control of an affected system. 
However, user interaction is required to exploit this vulnerability.

 Mitigating Factors for Task Scheduler Vulnerability - CAN-2004-0212: 

• In a Web-based attack scenario, an attacker would have to host a Web site 
that contains a Web page that is used to exploit this vulnerability. An 
attacker would have no way to force users to visit a malicious Web site. 
Instead, an attacker would have to persuade them to visit the Web site, 
typically by getting them to click a link that takes them to the attacker's 
site. An attack could only occur after they performed these actions.
 
• An attacker who successfully exploited this vulnerability could gain the 
same privileges as the user. Users whose accounts are configured to have 
fewer privileges on the system would be at less risk than users who operate 
with administrative privileges.
 
• Windows Server 2003 is not affected by this vulnerability. Windows NT 4.0 
is not vulnerable unless Internet Explorer 6 is installed. Internet Explorer 
6 is not affected when installed on other supported operating systems. 
Other versions Internet Explorer are not affected.
 

Top of section
 Workarounds for Task Scheduler Vulnerability - CAN-2004-0212: 

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.

• Do not open or save .job files that you receive from untrusted sources.
This vulnerability could be exploited when a user views a .job file. Do not 
open files that use this file name extension.

(added 7/19/04)
• Disable the dynamic icon handler for JobObject files by clearing the 
default value in the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\JobObject\shellex\IconHandler
 
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\SOFTWARE\Classes\JobObject\shellex\IconHandler
 
3.
 On the right windows pane you see a value of Default with Data of 
 {DD2110F0-9EEF-11cf-8D8E-00AA0060F5BF}.
 
4.
 Right click on Default and select Modify.
 
5.
 Clear out the Value Data listed and click OK.
 

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.

Impact of Workaround: Clearing the value of this key will prevent the 
possibility of attack by preventing the IconHandler from automatically 
parsing .job files. The files will no longer have an icon associated 
with them.



 

Top of section
 FAQ for Task Scheduler Vulnerability - CAN-2004-0212: 

What is the scope of the vulnerability?

This is a remote code execution vulnerability. If a user is logged on with 
administrative privileges, 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 with full privileges. Users whose accounts are configured to have 
fewer privileges on the system would be at less risk than users who operate 
with administrative privileges. However, user interaction is required to 
exploit this vulnerability.

What causes the vulnerability?

An unchecked buffer in the Task Scheduler component.

What is the Task Scheduler?

You can use Task Scheduler to schedule commands, programs, or scripts to 
run at specific times. A task is saved as a file that has a .job file name 
extension. This behavior makes it easier to move the task information from 
system to system. Administrators can create scheduled maintenance task files 
and put them where needed. For more information, see the Task Scheduler Web 
site.

What might an attacker use the vulnerability to do?

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.

How could an attacker exploit this vulnerability?

There are many ways that a system could be vulnerable to this attack. Here 
are some examples:

• An attacker could host a malicious Web site that is designed to exploit 
this vulnerability through Internet Explorer and then persuade a user to view 
the Web site.
 
• An attacker could add a specially crafted .job file to the local file 
system or to a network share and then persuade the user to view the folder 
by using Windows Explorer.
 
• An attacker could also access the affected component through another vector. 
For example, an attacker could log on to the system interactively or by using 
another program that passes parameters to the vulnerable component (locally 
or remotely).
 

What systems are primarily at risk from the vulnerability?

Workstations and terminal servers are primarily at risk. Servers are only at 
risk if users who do not have sufficient administrative credentials are 
given the ability to log on to servers and to run programs. However, best 
practices strongly discourage allowing this. 

Could the vulnerability be exploited over the Internet? 

Yes. An attacker could attempt to exploit this vulnerability over the Internet. 
Microsoft has provided information about how you can help protect your PC. 
End users can visit the Protect Your PC Web site. IT Professionals can visit 
the Security Guidance Center Web site.

What does the update do?

The update removes the vulnerability by modifying the way that Task Scheduler 
validates the length of a message before it passes the message to the 
allocated buffer.

When this security bulletin was issued, had this vulnerability been publicly 
disclosed?

No. Microsoft received information about this vulnerability through responsible 
disclosure. Microsoft had not received any information indicating that this 
vulnerability had been publicly disclosed when this security bulletin was 
originally issued.

When this security bulletin was issued, had Microsoft received any reports 
that this vulnerability was being exploited?

No. Microsoft had not received any information indicating that this 
vulnerability had been publicly used to attack customers and had not seen 
any examples of proof of concept code published when this security bulletin 
was originally issued.

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 XP (all versions) 

Note For Windows XP 64-Bit Edition Version 2003, this security update is 
the same as the Windows Server 2003 64-Bit Edition security update.

Prerequisites

This security update requires the release version of Windows XP or Windows 
XP Service Pack 1 (SP1). For more information, see Microsoft Knowledge 
Base Article 322389.

Inclusion in Future Service Packs:
The update for this issue will be included in Windows XP Service Pack 2.

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 XP:

Windowsxp-kb841873-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 XP:

Windowsxp-kb841873-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 is located in the %Windir%\$NTUninstallKB841873$\
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.

Windows XP Home Edition, Windows XP Professional, Windows XP Home Edition 
Service Pack 1, Windows XP Professional Service Pack 1, Windows XP Tablet 
PC Edition, and Windows XP Media Center Edition:

Date         Time   Version        Size     File name       Folder
-------------------------------------------------------------------
08-Jun-2004  22:01  5.1.2600.105    48,640  Browser.dll     RTMQFE
08-Jun-2004  22:01  5.1.2600.155   251,392  Mstask.dll      RTMQFE
03-Jun-2004  22:54  5.1.2600.155     9,728  Mstinit.exe     RTMQFE
08-Jun-2004  22:01  5.1.2600.122   301,568  Netapi32.dll    RTMQFE
08-Jun-2004  22:01  5.1.2600.155   159,232  Schedsvc.dll    RTMQFE
08-Jun-2004  22:02  5.1.2600.1564  260,096  Mstask.dll      SP1QFE
08-Jun-2004  19:59  5.1.2600.1564   10,752  Mstinit.exe     SP1QFE
08-Jun-2004  22:02  5.1.2600.1562  306,688  Netapi32.dll    SP1QFE
08-Jun-2004  22:02  5.1.2600.1564  172,544  Schedsvc.dll    SP1QFE
18-May-2004  03:46  5.1.2600.1555  593,408  Xpsp2res.dll    SP1QFE

Windows XP 64-Bit Edition Service Pack 1:

Date         Time   Version        Size     File name     Platform Folder
-------------------------------------------------------------------------------
05-Jun-2004  03:57  5.1.2600.1555     658,944  Mstask.dll   SP1QFE
18-May-2004  02:34  5.1.2600.1555      25,600  Mstinit.exe  SP1QFE
05-Jun-2004  03:57  5.1.2600.1562     905,728  Netapi32.dll SP1QFE
05-Jun-2004  03:57  5.1.2600.1555     576,000  Schedsvc.dll SP1QFE
18-May-2004  03:38  5.1.2600.1555     592,896  Xpsp2res.dll SP1QFE
05-Jun-2004  03:45  5.1.2600.1562     306,688  Wnetapi32.dll    SP1QFE\WOW
18-May-2004  03:46  5.1.2600.1555     593,408  Wxpsp2res.dll  SP1QFE\WOW

Notes The Windows XP versions of this security update are packaged as a 
dual-mode package, which contain files for both the original version of 
Windows XP and Windows XP Service Pack 1 (SP1). For more information about 
dual-mode packages, see Microsoft Knowledge Base Article 328848.

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, 
which 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 keys.

For Windows XP Home Edition, Windows XP Professional, Windows XP Home Edition 
Service Pack 1, Windows XP Professional Service Pack 1, Windows XP 64-Bit 
Edition Service Pack 1, Windows XP Tablet PC Edition, and Windows XP Media 
Center Edition:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows XP\SP2\KB841873\Filelist

For Windows XP 64-Bit Edition Version 2003:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows Server 2003\SP1\KB841873\
Filelist

Note These registry keys may not contain a complete list of installed files. 
Also, these registry keys may not be created correctly if an administrator 
or an OEM integrates or slipstreams the 841873 security update into the Windows 
installation source files.
 

Top of section

 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-kb841873-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-kb841873-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%\$NTUninstall
KB841873$\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. 
See the Verifying Update Installation section for details about 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
----------------------------------------------------------
24-Mar-2004  02:17  5.0.2195.6866   69,904  Browser.dll
10-Jun-2004  16:58  4.71.2195.6920 216,848  Mstask.dll
05-Apr-2004  17:51  4.71.2195.6920 119,568  Mstask.exe
10-Jun-2004  16:58  5.0.2195.6949  309,008  Netapi32.dll

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, which 
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\KB841873\
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 841873 security update into the 
Windows installation source files.
 

Top of section

 Internet Explorer 6 for Windows NT 4.0 SP6a 

Prerequisites

To install the Internet Explorer 6 version of this update, you must be 
running one of the following versions of Windows:

• Microsoft Windows NTฎ 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 6
 

Note Versions of Windows and versions of Internet Explorer that are not 
listed in this article are no longer supported or not affected. We 
recommend that you upgrade to a supported version of Windows and of Internet 
Explorer, and then apply the appropriate update.

For more information about support lifecycles for Windows components, see 
the following Microsoft Support Lifecycle Web site.

For more information about how to obtain the latest service pack for 
Internet Explorer 6, see Microsoft Knowledge Base Article 328548.

Installation Information 

The security update supports the following setup switches:

   /Q Specifies quiet mode, or suppresses prompts, when files are being 
      extracted. 

   /Q:U Specifies user-quiet mode, which presents some dialog boxes to the 
        user. 

   /Q:A Specifies administrator-quiet mode, which does not present any dialog 
        boxes to the user. 

   /T:  Specifies the target folder for extracting files. 

   /C Extracts the files without installing them. If /T: path is not specified, 
      you are prompted for a target folder. 

   /C:  Override Install Command defined by author. Specifies the path 
             and name of the Setup .inf or .exe file.

   /R:N Never restarts the computer after installation. 

   /R:I Prompts the user to restart the computer if a restart is required, 
        except when used with /Q:A. 

   /R:A Always restarts the computer after installation. 

   /R:S Restarts the computer after installation without prompting the user. 

   /N:V No version checking - Install the program over any previous version.

Note These switches do not necessarily work with all updates. If a switch is 
not available then that functionality is not necessary for the proper 
installation of the update. Also, the use of the /N:V switch is unsupported 
and may result in an unbootable system. If the installation is unsuccessful, 
you should consult your support professional to understand why it failed to 
install.

For additional information about the supported setup switches, see Microsoft 
Knowledge Base Article 197147.

Deployment Information

For example, to install the update without any user intervention and not 
force the system to restart, run the following command:

   IE-KB841873-WindowsNT4sp6-x86-ENU.exe /q:a /r:n

For information about how to deploy this security update with Software Update 
Services, visit the Software Update Services Web site.

Restart Requirements

In some cases, you do not have to restart your system after you apply this 
update. However, if the required files are in use, you must restart your 
system after you apply this update. If this behavior occurs, a message is 
displayed that advises you to restart your system. You do not have to use 
an administrator logon after the system restarts for any version of this u
pdate.

Removal Information

To remove this update, use the Add or Remove Programs tool (or the Add/
Remove Programs tool) in Control Panel. Click Internet Explorer Q841873, 
and then click Change/Remove (or click Add/Remove). 

System administrators can use the Ieuninst.exe utility to remove this 
update. This security update installs the Ieuninst.exe utility in the 
%Windir% folder. This utility supports the following setup switches: 

   /?: Show the list of supported switches 

   /z: Do not restart when the installation is complete 

   /q: Use Quiet mode (no user interaction) 

For example, to remove this update without any user intervention, use the  
following command: 

   c:\windows\ieuninst /q c:\windows\inf\q841873.inf

Note This command assumes that Windows is installed in the C:\Windows folder.

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. 

Date         Time   Version         Size     File name
--------------------------------------------------------
27-May-2004  19:52  4.71.1979.1     223,504  Mstask.dll


Verifying Update Installation 

• 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:

HKLM\Software\Microsoft\Active Setup\Installed Components\{bfb56e60-
5895-496c-bd6b-459b97142e4c}

Confirm that the IsInstalled DWORD value that has a data value of 1 
appears in the registry key.
 
• Program Version Verification 

Confirm that Q841873 is listed in the Update Versions field in the About 
Internet Explorer dialog box
 

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Top of section
Acknowledgments

Microsoft thanks the following for working with us to help protect customers:

• Brett Moore of 
Security-Assessment.com for reporting the Task Scheduler 
Vulnerability (CAN-2004-0212).
 
• Dustin Schneider for reporting the Task Scheduler Vulnerability 
(CAN-2004-0212).
 
• Peter Winter-Smith of Next Generation Security Software Ltd. for 
reporting the Task Scheduler Vulnerability (CAN-2004-0212).
 

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
• V1.1 (July 19, 2004): Bulletin updated with an additional workaround.
 

[***** End Microsoft Security Bulletin MS04-022 *****]


CIAC wishes to acknowledge the contributions of Microsoft Corporation for the information contained in this bulletin.
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