MS02-058: OLEXP: An Unchecked Buffer in Outlook Express S/MIME Parsing May Permit System Compromise

To permit Outlook Express to verify the authenticity of mail messages, Outlook Express supports digital signing of messages by using Secure/Multipurpose Internet Mail Extension (S/MIME). The code that generates a warning message when a particular error condition occurs contains a buffer overrun vulnerability. That error condition is associated with digital signatures.

If an attacker creates a digitally signed e-mail message, edits it to introduce specific data, and then sends it to another user, the attacker may cause one of two effects to occur when the recipient opens or previews the e-mail message:

• In the less serious case, the attacker may cause the mail client to stop responding. If this problem occurs, the recipient can restart the mail client, and then delete the offending mail to resume ordinary operation.
• In the more serious case, the attacker may cause the mail client to run code of the attacker's choice on the user's computer. Such code can take any action that the attacker wants, limited only by the permissions of the recipient on the computer.

This vulnerability only affects messages that are signed by using S/MIME and are sent to an Outlook Express user. Microsoft Outlook users are not affected by this vulnerability.

Outlook Express 6.0

The patch for this vulnerability is included with Microsoft Internet Explorer version 6 Service Pack 1 (SP1) and Microsoft Windows XP SP1. For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

Individual Patch Download Information

The following file is available for download from the Microsoft Download Center:

Release Date: October 10, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

Installation Information

This patch supports the following Setup switches:

• /q - Specifies quiet mode (in other words, suppresses prompts) when files are extracted.
• /q:u - Specifies user-quiet mode, which displays some dialog boxes to the user.
• /q:a - Specifies administrator-quiet mode, which does not display any dialog boxes to the user.
• /t:path - Specifies the target folder for extracting files.
• /c - Extracts the files without installing them.
• /c:path - Specifies the path and name of the Setup .inf or .exe file.
• /r:n - Never restarts the computer after an installation.
• /r:i - Restarts the computer if a restart is required. Automatically restarts the computer if a restart is required to complete installation.
• /r:a - Always restarts the computer after an installation.
• /r:s - Restarts the computer after an installation without prompting the user.
• /n:v - No version checking. Installs the program over any previous version.

For example, use the following command line to install the update without any user intervention and without forcing the computer to restart:

File Information

The English version of this fix 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: Because of file dependencies, this update may contain additional files.

Outlook Express 5.5

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that you determine are at risk of attack. Evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. See the associated Microsoft Security Bulletin (http://www.microsoft.com/technet/security/bulletin/MS02-058.mspx) to help determine the degree of risk. This fix may receive additional testing. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. Otherwise, wait for the next Internet Explorer 5.5 service pack that contains this fix.

To resolve this problem immediately, download the fix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Download Information

The following file is available for download from the Microsoft Download Center:
Release Date: October 10, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on secure servers that prevent any unauthorized changes to the file.

Installation Information

This patch requires Internet Explorer 5.5 Service Pack 2 (SP2). For additional information, click the article number below to view the article in the Microsoft Knowledge Base: This patch supports the following Setup switches:

• /q - Specifies quiet mode (in other words, suppresses prompts) when files are extracted.
• /q:u - Specifies user-quiet mode, which displays some dialog boxes to the user.
• /q:a - Specifies administrator-quiet mode, which does not display any dialog boxes to the user.
• /t:path - Specifies the target folder for extracting files.
• /c - Extracts the files without installing them.
• /c:path - Specifies the path and name of the Setup .inf or .exe file.
• /r:n - Never restarts the computer after an installation.
• /r:i - Restarts the computer if a restart is required. Automatically restarts the computer if a restart is required to complete installation.
• /r:a - Always restarts the computer after an installation.
• /r:s - Restarts the computer after an installation without prompting the user.
• /n:v - No version checking. Installs the program over any previous version.

For example, use the following command line to install the update without any user intervention and without forcing the computer to restart:

File Information

The English version of this fix 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: Because of file dependencies, this update may contain additional files.

Microsoft has confirmed that this problem may cause a degree of security vulnerability in the Microsoft products that are listed at the beginning of this article.

For additional information about this vulnerability, visit the following Microsoft Web site: For additional information about what this patch fixes, click the article number below to view the article in the Microsoft Knowledge Base: