Public Vulnerability Reports

Microsoft Exchange Server 2000 IMAP Literal Processing DoS Vulnerability



Microsoft Exchange Server 2000 is a messaging product developed by Microsoft, part of the Windows Server System line of server products. More information about it can be found at the following URL.


Remote exploitation of an integer overflow vulnerability in the IMAP service of Microsoft Exchange 2000 could allow a remote attacker to crash all running Exchange services and other services in the same process.

The vulnerability specifically exists in code responsible for reading of literals in the IMAP4 service. When the IMAP4 service encounters a specially crafted literal, it fails to properly process it. An access violation occurs causing an unhandled exception that terminates the process.


Exploitation of this vulnerability allows an attacker to cause the affected server to restart or potentially require data to be reinstalled from backup.

As the Exchange server may run in the same process space as many other servers, crashing the IMAP4 component will also cause the SMTP, POP3, WWW and FTP services, if enabled, to exit. In order to exploit this vulnerability, the attacker must have access to establish a TCP session with the IMAP4 service.


iDefense confirmed the existence of this vulnerability in Microsoft Exchange 2000 with Service Pack 3.


iDefense is not currently aware of any effective workarounds for this vulnerability. Consider applying network access controls on this service.


Microsoft has addressed this vulnerability within MS07-026. For more information, consult their bulletin at the following URL.


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-0221 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


01/10/2007 Initial vendor notification
01/22/2007 Initial vendor response
05/08/2007 Coordinated public disclosure


This vulnerability was reported to iDefense by Joxean Koret.

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Copyright © 2007 Verisign, Inc.

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