The following is a Security Bulletin from the Microsoft Product Security Notification Service. Please do not reply to this message, as it was sent from an unattended mailbox. ******************************** -----BEGIN PGP SIGNED MESSAGE----- - ---------------------------------------------------------------------- Title: Incorrect Attachment Handling in Exchange OWA Can Execute Script Released: 06 June 2001 Revised: 08 June 2001 (version 2.0) Software: Exchange 5.5, Exchange 2000 Impact: Run code of attacker's choice on mail client Bulletin: MS01-030 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-030.asp. - ---------------------------------------------------------------------- Reason for Revision: ==================== - Exchange 5.5 has been determined to be affected by the vulnerability. We have developed an Exchange 5.5 patch. - The originally released Exchange 2000 patch has been determined to contain a regression error that can cause performance problems on the servers it is installed on. We have eliminated the regression error and updated the patch; we recommend that customers who installed the original patch install the updated one. Issue: ====== OWA is a service of Exchange Server that allows users to use a web browser to access their Exchange mailbox. However, a flaw exists in the interaction between OWA and IE for message attachments. If an attachment contains HTML code including script, the script will be executed when the attachment is opened, regardless of the attachment type. Because OWA requires that scripting be enabled in the zone where the OWA server is located, this script could take action against the user's Exchange mailbox. An attacker could use this flaw to construct an attachment containing malicious script code. The attacker could then send the attachment in a message to the user. If the user opened the attachment in OWA, the script would execute and could take action against the user's mailbox as if it were the user, including, under certain circumstances, manipulation of messages or folders. Mitigating Factors: ==================== - The vulnerability could only be exploited if the user were using OWA in conjunction with IE. - The vulnerability is only exploitable by attachments that are received via OWA. In general, an attacker would have no way to determine whether a user would open an attachment using OWA rather than an Outlook client. - An attacker's ability to exploit this vulnerability would require that she entice the user to open an attachment from an untrusted source. Best practices recommend against opening any attachment from an unknown or untrusted source. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-030.asp for information on obtaining this patch. Acknowledgment: =============== - Joao Gouveia ([EMAIL PROTECTED]) - --------------------------------------------------------------------- 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. 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