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Category:   Application (E-mail Server)  >   Exim Vendors:   Exim.org
Exim Heap Overflow in 'smtp_in.c' May Allow Remote Arbitrary Code Execution
SecurityTracker Alert ID:  1007609
SecurityTracker URL:  http://securitytracker.com/id/1007609
CVE Reference:   CVE-2003-0743   (Links to External Site)
Updated:  Sep 5 2003
Original Entry Date:  Sep 3 2003
Impact:   Denial of service via network, Execution of arbitrary code via network, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 3, 4 (prior to 4.21)
Description:   A vulnerability was reported in the Exim mail transfer agent. A remote user can trigger a heap overflow.

It is reported that a remote user can connect to the target system via the SMTP port and send specially crafted data to trigger a heap overflow. According to the report, the overflow is "probably not exploitable," but the report admits that this statement may be proven false on some platforms and in some situations.

The flaw resides in 'smtp_in.c' in the processing of HELO strings.

Impact:   A remote user may be able to execute arbitrary code on the system (however, that was not confirmed in the report).
Solution:   The vendor has released a fixed version (4.21), available at:

http://www.exim.org/mirrors.html

Also, patches for Exim 4.20 and Exim 3.36 are available at:

http://www.exim.org/pipermail/exim-announce/2003q3/000094.html

Vendor URL:  www.exim.org/pipermail/exim-announce/2003q3/000094.html (Links to External Site)
Cause:   Boundary error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   This archive entry has one or more follow-up message(s) listed below.
Sep 5 2003 (Debian Issues Fix) Exim Heap Overflow in 'smtp_in.c' May Allow Remote Arbitrary Code Execution
Debian has released a fix for exim and exim-tls.
Sep 5 2003 (Conectiva Issues Fix) Exim Heap Overflow in 'smtp_in.c' May Allow Remote Arbitrary Code Execution
Conectiva has released a fix.
Sep 8 2003 (Debian Issues Revised Fix) Exim Heap Overflow in 'smtp_in.c' May Allow Remote Arbitrary Code Execution
Debian has released a revised fix to correct the previous fix.



 Source Message Contents

Subject:  exim remote heap overflow, probably not exploitable



Exim (www.exim.org) is a message transfer agent (MTA) developed
at the University of Cambridge for use on Unix systems connected
to the Internet.

There's a heap overflow in all versions of exim3 and exim4 prior
to version 4.21.  It can be exercised by anyone who can make an
SMTP connection to the exim daemon.

The overflow is very limited, and in my opinion it's probably not
exploitable.  However, it's possible that this will prove to be
exploitable for arbitrary command execution on some platforms in
some circumstances.

Patches:

  http://www.exim.org/pipermail/exim-announce/2003q3/000094.html

Full details coming soon to vuln-dev.

--
Nick Cleaton
nick@cleaton.net

 
 


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