-----BEGIN PGP SIGNED MESSAGE----- =============================================================================== Security Advisory CERT-NL =============================================================================== Author/Source : Niels den Otter Index : S-99-27 Distribution : World Page : 1 Classification: External Version: 1 Subject : Microsoft vuln. in Exchange(r) Server Date : 16-Aug-99 =============================================================================== By courtesy of The U.S. Department of Energy Computer Incident Advisory Capability we received information on a vulnerability in the Microsoft Exchange Server 5.5 software. The vulnerability could allow an attacker to perform mail relaying via an Exchange server that is configured to act as a gateway for other Exchange sites using the Internet Messaging Service. CERT-NL recommends applying the patch described below. ============================================================================== __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft "Encapsulated SMTP Address" Vulnerability August 10, 1999 17:00 GMT Number J-056 ______________________________________________________________________________ PROBLEM: Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Exchange(r) Server. PLATFORM: Microsoft Exchange Server 5.5 DAMAGE: The vulnerability could allow an attacker to perform mail relaying via an Exchange server that is configured to act as a gateway for other Exchange sites using the Internet Messaging Service. SOLUTION: Apply patches listed below ______________________________________________________________________________ VULNERABILITY Risk is medium. This vulnerability could allow encapsulated ASSESSMENT: SMTP addresses to be used to send mail to any desired e-mail Address. ______________________________________________________________________________ [ Start Microsoft Advisory ] Microsoft Security Bulletin (MS99-027) - - -------------------------------------- Patch Available for "Encapsulated SMTP Address" Vulnerability Originally Posted: August 06, 1999 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Exchange(r) Server. The vulnerability could allow an attacker to perform mail relaying via an Exchange server that is configured to act as a gateway for other Exchange sites using the Internet Messaging Service. Frequently asked questions regarding this vulnerability can be found at http://www.microsoft.com/security/bulletins/MS99-027faq.asp Issue ===== Exchange Server implements features designed to defeat "mail relaying", a practice in which an attacker causes an e-mail server to forward mail from the attacker, as though the server were the sender of the mail. However, a vulnerability exists in this feature, and could allow an attacker to circumvent the anti-relaying features in an Internet-connected Exchange Server. The vulnerability lies in the way that site-to-site relaying is performed via SMTP. Encapsulated SMTP addresses could be used to send mail to any desired e-mail address. The patch eliminates the vulnerability by making encapsulated SMTP addresses subject to the same anti-relay protections as non-encapsulated SMTP addresses. Affected Software Versions ========================== - Microsoft Exchange Server 5.5 Patch Availability ================== - ftp://ftp.microsoft.com/bussys/exchange/exchange-public /fixes/Eng/Exchg5.5/PostSP2/imc-fix NOTE: Line breaks have been inserted into the above URL for readability. More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin MS99-027: Frequently Asked Questions, http://www.microsoft.com/security/bulletins/MS99-027faq.asp. - Microsoft Knowledge Base (KB) article Q237927, XIMS: Messages Sent to Encapsulated SMTP Address Are Rerouted Even Though Rerouting Is Disabled, http://support.microsoft.com/support/kb/articles/q237/9/27.asp. - Microsoft Security Advisor web site, http://www.microsoft.com/security/default.asp. Obtaining Support on this Issue =============================== This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/support/contact/default.asp. Acknowledgments =============== Microsoft acknowledges Laurent Frinking of Quark Deutschland GmbH for bringing this issue to our attention and working with us to alert customers about it. Revisions ========= - August 06, 1999: Bulletin Created. - - ----------------------------------------------------------------------- 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. (c) 1999 Microsoft Corporation. All rights reserved. ******************************************************************* You have received this e-mail bulletin as a result of your registration to the Microsoft Product Security Notification Service. You may unsubscribe from this e-mail notification service at any time by sending an e-mail to MICROSOFT_SECURITY-SIGNOFF-REQUEST@ANNOUNCE.MICROSOFT.COM The subject line and message body are not used in processing the request, and can be anything you like. For more information on the Microsoft Security Notification Service please visit http://www.microsoft.com/security/services/bulletin.asp. For security-related information about Microsoft products, please visit the Microsoft Security Advisor web site at http://www.microsoft.com/security. [ End Microsoft Advisory ] ______________________________________________________________________________ CIAC wishes to acknowledge Microsoft for the information contained in this bulletin. ______________________________________________________________________________ ============================================================================== CERT-NL is the Computer Emergency Response Team for SURFnet customers. SURFnet is the Dutch network for educational, research and related institutes. CERT-NL is a member of the Forum of Incident Response and Security Teams (FIRST). All CERT-NL material is available under: http://www.surfnet.nl/surfnet/security/cert-nl.html ftp://ftp.surfnet.nl/surfnet/net-security In case of computer or network security problems please contact your local CERT/security-team or CERT-NL (if your institute is NOT a SURFnet customer please address the appropriate (local) CERT/security-team). 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CERT-NL WILL THEN CONTACT YOU. ============================================================================== -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: latin1 iQCVAwUBN7h5hvE6s6q7Tf4RAQGMowQAmv+BaqtFq2cfPNRxgXrXsiykWfwsvqX+ dSGiksvMwQ2EulOCh61PL7QchwqH36BZwqGcLr0XSB7wNN77ScTrMABmy3h9r3hI 3Uj5FF1O/GwcMHHx6Q7aQ97uubgHqJAGGh8qqt7ESCoc3B1XKguGqVF7CATvjK4O PMB0lo7ivLA= =58Xl -----END PGP SIGNATURE-----