Microsoft Security Bulletin MS99-027 - Critical
Patch Available for "Encapsulated SMTP Address" Vulnerability
Published: August 06, 1999 | Updated: March 21, 2003
Patch Availability Information Updated: March 21, 2003
Originally Posted: August 06, 1999
Microsoft has released a patch that eliminates a security vulnerability in Microsoft® Exchange® 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/technet/security/bulletin/fq99-027.mspx
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
Vulnerability Identifier: CVE-1999-0682
Please see the following references for more information related to this issue.
- Microsoft Security Bulletin MS99-027: Frequently Asked Questions, http://www.microsoft.com/technet/security/bulletin/fq99-027.mspx.
- Microsoft Knowledge Base (KB) article 237927, XIMS: Messages Sent to Encapsulated SMTP Address Are Rerouted Even Though Rerouting Is Disabled, http://support.microsoft.com/default.aspx?scid=kb;en-us;237927&sd=tech.
- Microsoft Security web site, http://www.microsoft.com/technet/security/default.mspx.
- IIS Security Checklist, http://www.microsoft.com/technet/security/chklist/iischk.mspx.
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/contactussupport/?ws=support.
Microsoft acknowledges Laurent Frinking of Quark Deutschland GmbH for bringing this issue to our attention and working with us to alert customers about it.
- August 06, 1999: Bulletin Created.
- V2.0 (March 21, 2003): Introduced versioning and updated patch availability information.
For additional security-related information about Microsoft products, please visit http://www.microsoft.com/technet/security
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