DOCUMENT:Q301361 08-MAY-2002 [exchange] TITLE :XGEN: Incorrect Attachment Processing in Exchange Server 5.5 OWA PRODUCT :Microsoft Exchange PROD/VER::5.5,5.5 SP1,5.5 SP2,5.5 SP3,5.5 SP4 OPER/SYS: KEYWORDS:kbExchange550preSP5fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Exchange Server, versions 5.5, 5.5 SP1, 5.5 SP2, 5.5 SP3, 5.5 SP4 ------------------------------------------------------------------------------- For additional information about a similar problem that can occur in Exchange 2000 Server, click the article number below to view the article in the Microsoft Knowledge Base: Q299535 XGEN: Incorrect Attachment Processing in Exchange 2000 Outlook Web Access Can Run Script SYMPTOMS ======== Microsoft Outlook Web Access (OWA) is a service of Exchange Server 5.5 and Exchange 2000 Server that a user can use to gain access to an Exchange mailbox by using a Web browser. However, 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. RESOLUTION ========== A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems that are determined to be at risk of attack. Please evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. Please see the associated Microsoft Security Bulletin (http://www.microsoft.com/technet/security/bulletin/MS01-030.asp) to help make this determination. This fix may receive additional testing at a later time, to further ensure product quality. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. Otherwise, wait for the next Microsoft Exchange Server 5.5 service pack that contains this fix. To resolve this problem immediately, download the fix as instructed below or contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web: http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The following files are available for download from the Microsoft Download Center: DownloadDownload Q301361i386.exe now (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=30568) Release Date: June 8, 2001 For additional information about how to download Microsoft Support files, click the article number below to view the article in the Microsoft Knowledge Base: Q119591 How to Obtain Microsoft Support Files from Online Services Microsoft used the most current virus detection software available on the date of posting to scan this file for viruses. After it is posted, the file is housed on secure servers that prevent any unauthorized changes to the file. The English version of this fix should have the following file attributes or later: Component: OWA +---------------------+ | File name | Version | +---------------------+ | Read.asp | na | +---------------------+ NOTES - Because of file dependencies, this fix requires Microsoft Exchange Server version 5.5 Service Pack 4. - You need to apply this fix to all servers that run the OWA components. With Exchange Server 5.5, you can install the OWA components on a computer that is separate from the Exchange Server. If you install OWA separately, you need to run this patch on the separate computer. - Sometimes, after applying this fix, users may get a blank window when they open their messages using OWA. If this occurs, please review the following Knowledge Base article Q314532 XWEB: Troubleshooting Blank Message Bodies in Outlook Web STATUS ====== Microsoft has confirmed that this problem could result in some degree of security vulnerability in Microsoft Exchange Server version 5.5. MORE INFORMATION ================ For more information about this security vulnerability, see the following Microsoft Web site: http://www.microsoft.com/technet/security/bulletin/MS01-030.asp Additional query words: security_patch ====================================================================== Keywords : kbExchange550preSP5fix Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 kbExchange550SP1 kbExchange550SP2 kbExchange550SP3 kbExchange550SP4 Version : :5.5,5.5 SP1,5.5 SP2,5.5 SP3,5.5 SP4 Issue type : kbbug Solution Type : kbfix ============================================================================= 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. Copyright Microsoft Corporation 2002.