Vulnerability Note VU#869640

Microsoft Outlook Express fails to properly validate malformed e-mail headers

Overview

A vulnerability exists in some versions of Microsoft Outlook Express that could allow a remote attacker to cause a denial of service.

I. Description

According to Microsoft Security Bulletin MS04-018, a flaw exists in the way that some versions of Microsoft's Outlook Express mail client validate message headers. This flaw results in a vulnerability that could cause the Outlook Express program to crash when an email message containing certain malformed headers are received. The specific nature of the malformation is not known at this time.

Microsoft's bulletin states that the following versions of Outlook Express are affected by this issue:

Microsoft Outlook Express 5.5 Service Pack 2
Microsoft Outlook Express 6
Microsoft Outlook Express 6 Service Pack 1
Microsoft Outlook Express 6 Service Pack 1 (64 bit Edition)
Microsoft Outlook Express 6 on Windows Server 2003
Microsoft Outlook Express 6 on Windows Server 2003 (64 bit edition)

II. Impact

An attacker with the ability to craft and deliver a specially-formed email message could cause the Outlook Express program on the recipient's computer to crash.

III. Solution

Apply a patch from the vendor

Microsoft has released patches to address this issue. Please see the Systems Affected section of this document for more information.

Workarounds

Microsoft lists the following partial workaround for this vulnerability:

Disable the preview pane

Disabling the preview pane will prevent the malicious e-mail message from causing Outlook Express to fail on each restart. To disable the preview pane, follow these steps:

1.	In Outlook Express, click View, and then click Layout.
2.	Click to clear the Show Preview Pane check box, and then click OK.

Note that this workaround will not mitigate the vulnerability, but will prevent the malicious e-mail message from causing Outlook Express to fail on each restart.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Microsoft Corporation	Vulnerable	14-Jul-2004

References

http://www.microsoft.com/technet/security/bulletin/MS04-018.mspx

Credit

Thanks to Microsoft Security for reporting this vulnerability.

This document was written by Chad R Dougherty based upon information provided in Microsoft Security Bulletin MS04-018.

Other Information

Date Public:	2004-07-13
Date First Published:	2004-07-14
Date Last Updated:	2004-07-23
CERT Advisory:
CVE-ID(s):	CAN-2004-0215
NVD-ID(s):	CAN-2004-0215
US-CERT Technical Alerts:
Metric:	7.48
Document Revision:	16

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