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iDEFENSE Security Advisory 05.25.05: GNU Mailutils 0.6 imap4d fetch_io Heap overflow Vulnerability
From: "iDEFENSE Labs" <labs-no-reply () idefense com>
Date: Wed, 25 May 2005 13:25:31 -0400

GNU Mailutils 0.6 imap4d fetch_io Heap overflow Vulnerability 

iDEFENSE Security Advisory 05.25.05
May 25, 2005


The GNU mailutils package is a collection of mail-related
utilities, including local and remote mailbox access services.
More information is available at the following site:



Remote exploitation of an integer overflow in the fetch_io
function of the imap4d server from the GNU Project's Mailutils
package error may allow an authenticated remote attacker to 
execute arbitrary code.

The imap4d server allows remote users to retrieve their email
via the Internet Message Access Protocol, version 4rev1 as
specified in RFC3501. This is a client/server protocol supported
by a large number of email clients on multiple platforms.

The vulnerability specifically exists in the handling of partial
message requests. By supplying a value for the 'END' parameter
equal to 2 less than the largest value an integer on the
affected system can hold, it is possible to cause the server to
allocate a much smaller chunk of memory. An overflow can occur
when this memory chunk is referenced.


Successful exploitation of this vulnerability could allow a
remote authenticated used execute arbitrary commands in the
context of the 'daemon' user. As the service is forked from a
parent process, it would be possible for a remote attacker to
attempt to exploit this vulnerability multiple times, although
each failed attempt which caused a crash would be logged.


iDEFENSE Labs has verified the existance of this vulnerability
in versions 0.5 and 0.6 of the GNU Mailutils package. It is
suspected that any previous versions which contain the imap4d
server are also affected.


iDEFENSE is currently unaware of any effective workarounds for
this issue. Access to the affected host should be filtered at
the network boundary if global accessibility is not required.
Restricting access to only trusted hosts and networks may reduce
the likelihood of exploitation.


This vulnerability has been fixed in GNU mailutils 0.6.90 which is
available for download at:



The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-1521 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.


05/12/2005  Initial vendor notification
05/12/2005  Initial vendor response
05/25/2005  Public disclosure


infamous41md () hotpop com is credited with the discovery of this

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Copyright (c) 2005 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDEFENSE. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email customerservice () idefense com for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.

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