XGEN: Incorrect Attachment Processing in Exchange 2000 Outlook Web Access Can Run Script

This article was previously published under Q299535
This article has been archived. It is offered "as is" and will no longer be updated.
On June 06, 2001 Microsoft released the original version of this patch. Microsoft subsequently identified two issues that necessitated updating the patch on June 08, 2001:
  • The vulnerability was found to affect Microsoft Exchange Server 5.5. Microsoft has developed a patch that eliminates the vulnerability, and recommends that customers that offer Microsoft Outlook Web Access (OWA) services by using Exchange Server 5.5 install this patch.For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
    301361 XGEN: Incorrect Attachment Processing in Exchange Server 5.5 Outlook Web Access Can Run Script
  • A regression error was identified in the patch that was originally provided for Exchange 2000. Microsoft has corrected the error and provided an updated version of the patch. Microsoft recommends that customers who installed the original version of the Exchange 2000 patch install the updated version.
OWA is a service of Exchange 2000 Server that a user can use to gain access to an Exchange mailbox by using a Web browser. However, a vulnerability exists in the interaction between OWA and Microsoft Internet Explorer for message attachments. If an attachment contains Hypertext Markup Language (HTML) code that includes script, the script is run when the user opens the attachment, regardless of the attachment type. Because OWA requires that scripting be enabled in the zone where the OWA server is located, this script can take action against the user's Exchange mailbox.

An attacker might use this vulnerability to construct an attachment that contains malicious script code. The attacker can then send the attachment in a message to a user. If the user opens the attachment in OWA, the script runs and can take action against the user’s mailbox as if the script is the user, including, under certain circumstances, manipulation of messages or folders.

The following are mitigating factors:
  • The vulnerability can only be exploited if the user is using OWA in conjunction with Internet Explorer.
  • The vulnerability can only be exploited by attachments that are received by using OWA. In general, an attacker has no way to determine whether a user will open an attachment by using OWA rather than Microsoft Outlook.
  • An attacker's ability to exploit this vulnerability requires that the attacker entice the user to open an attachment from an untrusted source. The best practice is not to open any attachment from an unknown or untrusted source.
The following files are available for download from the MicrosoftDownload Center:
Release Date: June 8, 2001

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
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.To resolve this problem, obtain the latest service pack for Microsoft Exchange 2000 Server. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
301378 XGEN: How to Obtain the Latest Exchange 2000 Server Service Pack
The English version of this fix should have the following file attributes or later:

Component: OWA

File nameVersion

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Microsoft Exchange 2000 Server.

This problem was first corrected in Microsoft Exchange 2000 Server Service Pack 1.
For more information about this security vulnerability, see the following Microsoft Web site:
security_patch Execute

Article ID: 299535 - Last Review: 10/23/2013 20:00:42 - Revision: 3.4

Microsoft Exchange 2000 Server Standard Edition

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