Unchecked Buffer in Outlook Express New

A security vulnerability in Outlook Express S/MIME parsing could allow a remote attacker to compromise the system by running the code of their choice.

Issue

To allow for verification of the authenticity of mail messages, Microsoft Outlook Express supports digital signing of messages through S/MIME. A buffer overrun vulnerability lies in the code that generates the warning message when a particular error condition associated with digital signatures occurs.

By creating a digitally signed email and editing it to introduce specific data, then sending it to another user, an attacker could cause either of two effects to occur if the recipient opened or previewed it. In the less serious case, the attacker could cause the mail client to fail. If this happened, the recipient could resume normal operation by restarting the mail client and deleting the offending mail. In the more serious case, the attacker could cause the mail client to run code of their choice on the user’s machine. Such code could take any desired action, limited only by the permissions of the recipient on the machine.

This vulnerability could only affect messages that are signed using S/MIME and sent to an Outlook Express user. Users of Microsoft Outlook products are not affected by this vulnerability.

Affected Products

• Microsoft Outlook Express 6.0
• Microsoft Outlook Express 5.5

Download

Patch: http://www.microsoft.com/windows/ie/downloads/critical/q328676/default.asp

Further Details

Source: Microsoft Corporation

Reference: Microsoft Corporation

Updated: October 11, 2002

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