-----BEGIN PGP SIGNED MESSAGE-----

===========================================================================
              AUSCERT External Security Bulletin Redistribution
                             
              ESB-2000.276 -- Cisco Security Advisory (Revised)
              Cisco Secure PIX Firewall Mailguard Vulnerability
                               10 October 2000

===========================================================================

	AusCERT Security Bulletin Summary
	---------------------------------

Product:                Cisco Secure PIX Firewall
Vendor:                 Cisco Systems
Impact:                 Reduced Security
Access Required:        Remote
Ref:                    ESB-2000.268

- --------------------------BEGIN INCLUDED TEXT--------------------

- -----BEGIN PGP SIGNED MESSAGE-----

   
Cisco Security Advisory: Cisco Secure PIX Firewall Mailguard Vulnerability

Revision 1.1
                                       
Updated, for public release 2000 October 5 04:00 PM US/Pacific (UTC+0700)
     _________________________________________________________________
   
Summary

   The Cisco Secure PIX firewall feature "mailguard," which limits SMTP
   commands to a specified minimum set of commands, can be bypassed.
   
   This vulnerability can be exploited to bypass SMTP command filtering.
   
   This vulnerability has been assigned Cisco bug ID CSCdr91002 and
   CSCds30699.

   A new aspect of this vulnerability has been assigned Cisco bug ID 
   CSCds38708.
   
   The complete advisory is available at
   http://www.cisco.com/warp/public/707/PIXfirewallSMTPfilter-pub.shtml.
   
Affected Products

   All users of Cisco Secure PIX Firewalls with software versions up to
   and including 4.4(6), 5.0(3), 5.1(3) and 5.2(2) that provide access to
   SMTP Mail services are at risk.
   
   The IOS Firewall featureset is not affected by either of the above
   defects.
   
Details

   The behavior is a failure of the command "fixup protocol smtp
   [portnum]", which is enabled by default on the Cisco Secure PIX
   Firewall.
   
   If you do not have protected Mail hosts with the accompanying
   configuration (configuration example below) you are not affected by
   this vulnerability.
   
   To exploit this vulnerability, attackers must be able to make
   connections to an SMTP mail server protected by the PIX Firewall.  If
   your Cisco Secure PIX Firewall has configuration lines similar to the
   following:
   
             fixup protocol smtp 25
   
   and either
   
             conduit permit tcp host 192.168.0.1 eq 25 any
   
   or
   
             conduit permit tcp 192.168.0.1 255.255.255.0 eq 25 any
   
   or
   
             access-list 100 permit tcp any host 192.168.0.1 eq 25
             access-group 100 in interface outside
   
   The expected filtering of the Mailguard feature can be circumvented by
   an attacker.
   
  Impact
  
   The Mailguard feature is intended to help protect weakly secured mail
   servers.  The workaround for this issue is to secure the mail servers
   themselves, or upgrade to fixed PIX firewall code.
   
   In order to exploit this vulnerability, an attacker would need to also
   exploit the mailserver that is currently protected by the PIX.  If
   that server is already well configured, and has the latest security
   patches and fixes from the SMTP vendor, that will minimize the
   potential for exploitation of this vulnerability.
   
Software Versions and Fixes

  Getting Fixed Software
  
   Cisco is offering free software upgrades to remedy this vulnerability
   for all affected customers. Customers with service contracts may
   upgrade to any software version. Customers without contracts may
   upgrade only within a single row of the table below, except that any
   available fixed software will be provided to any customer who can use
   it and for whom the standard fixed software is not yet available. As
   always, customers may install only the feature sets they have
   purchased.
   
   +-------------------------------------+----------------------------------+
   |                                     | Fixed Regular Release available  |
   | Version Affected                    | now; fix will carry forward into |
   |                                     | all later releases               |
   +-------------------------------------+----------------------------------+
   | All versions of Cisco Secure PIX up |                                  |
   | to version 4.4(6) (including 2.7,   | 4.4(7)                           |
   | 3.0, 3.1, 4.0, 4.1)                 |                                  |
   +-------------------------------------+----------------------------------+
   | Version 5.0.x up to and including   |                                  |
   | version 5.0(3)                      | 5.1(4)                           |
   +-------------------------------------+----------------------------------+
   | All 5.1.x up to and including       |                                  |
   | version 5.1(3)*                     | 5.1(4)                           |
   +-------------------------------------+----------------------------------+
   | Version 5.2(2)                      | 5.2(3)                           |
   +-------------------------------------+----------------------------------+
   
   *For customers who may have engineering releases addressing specific
   unrelated defects, designated as 5.1(2)2xx, version 5.1(4) only
   includes the SMTP security fixes and does not include any other
   bugfixes. Customers requiring engineering releases to address specific
   unrelated defects will need to use 5.1.4(200) or 4.4.7(200), which 
   include all SMTP vulnerability fixes.
   
   Customers with contracts should obtain upgraded software through their
   regular update channels. For most customers, this means that upgrades
   should be obtained via the Software Center on Cisco's Worldwide Web
   site at http://www.cisco.com.
   
   Customers without contracts should get their upgrades by contacting
   the Cisco Technical Assistance Center (TAC). TAC contacts are as
   follows:
     * +1 800 553 2447 (toll-free from within North America)
     * +1 408 526 7209 (toll call from anywhere in the world)
     * e-mail: tac@cisco.com
       
   Give the URL of this notice as evidence of your entitlement to a free
   upgrade. Free upgrades for non-contract customers must be requested
   through the TAC. Please do not contact either "psirt@cisco.com" or
   "security-alert@cisco.com" for software upgrades.
   
Workarounds

   There is not a direct work around for this vulnerability.  The
   potential for exploitation can be lessened by ensuring that mail
   servers are secured without relying on the PIX functionality.
   
Exploitation and Public Announcements

   This vulnerability was first reported to Cisco by a customer.  This
   vulnerability has been discussed on public forums.
   
Status of This Notice: Revised FINAL

   This is a final field notice. Although Cisco cannot guarantee the
   accuracy of all statements in this notice, all of the facts have been
   checked to the best of our ability.   Cisco does not anticipate
   issuing updated versions of this notice unless there is some material
   change in the facts. Should there be a significant change in the
   facts, Cisco may update this notice.
   
Distribution
  
   This notice will be posted on Cisco's Worldwide Web site at
   http://www.cisco.com/warp/public/707/PIXfirewallSMTPfilter-pub.shtml.
   In addition to Worldwide Web posting, a text version of this notice is
   clear-signed with the Cisco PSIRT PGP key and is posted to the
   following e-mail and Usenet news recipients:
     * cust-security-announce@cisco.com
     * bugtraq@securityfocus.com
     * first-teams@first.org (includes CERT/CC)
     * cisco@spot.colorado.edu
     * comp.dcom.sys.cisco
     * firewalls@lists.gnac.com
     * Various internal Cisco mailing lists
       
   Future updates of this notice, if any, will be placed on Cisco's
   Worldwide Web server, but may or may not be actively announced on
   mailing lists or newsgroups. Users concerned about this problem are
   encouraged to check the URL given above for any updates.
   
Revision History
   
   Revision 1.1  05-OCT-2000  New defect ID reference, and revised the Fixed
in versions to
                              reflect recent fixes.
   Revision 1.0  27-SEP-2000  Initial Public Release
   
Cisco Security Procedures

   Complete information on reporting security vulnerabilities in Cisco
   products, obtaining assistance with security incidents, and
   registering to receive security information from Cisco, is available
   on Cisco's Worldwide Web site at
   http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This
   includes instructions for press inquiries regarding Cisco security
   notices.
     _________________________________________________________________
   
   This notice is copyright 2000 by Cisco Systems, Inc. This notice may
   be redistributed freely after the release date given at the top of the
   text, provided that redistributed copies are complete and unmodified,
   including all date and version information.
     _________________________________________________________________
   
- -----BEGIN PGP SIGNATURE-----
Version: PGP 6.0.2

iQEVAwUBOd3/8WiN3BRdFxkbAQEPLwf+LIbWNxHUs+HMMHR6tO2bkKmO/d32zv08
zgx/HaaPe7bufQbr7quVtzsJvsBInbWv3Nw7d5nUN2PJb2YYVTStYNXEmUUP2zNS
2vOp+b7+BbBGLTH75Lg95c/PaU50hsRIc++J511EJ6EJuAJ0cpzSV/jLGC8EFk+8
s/gtfWNwxA039zX88heXvpF4r610UgUHkZaBIBisXLRSG6o9SAworB8t+TAtNrMh
M9tAemxKSeUOHaO7lMppJeckWLSCnOJtR20SDzAB2k5kR34QNw1vNQftKZTriE3m
kMqVYIPZEymPJosYPaetldHveKEJskYnBAqBLnYHAwzLqn16rVJCVQ==
=VBb3
- -----END PGP SIGNATURE-----

- --------------------------END INCLUDED TEXT--------------------

This security bulletin is provided as a service to AusCERT's members.  As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content.  The decision to use any or all of this information is
the responsibility of each user or organisation, and should be done so in
accordance with site policies and procedures.

NOTE: This is only the original release of the security bulletin.  It may
not be updated when updates to the original are made.  If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the original authors to ensure that the information is still current.

Contact information for the authors of the original document is included
in the Security Bulletin above.  If you have any questions or need further
information, please contact them directly.

Previous advisories and external security bulletins can be retrieved from:

	http://www.auscert.org.au/Information/advisories.html

If you believe that your system has been compromised, contact AusCERT or
your representative in FIRST (Forum of Incident Response and Security
Teams).

Internet Email: auscert@auscert.org.au
Facsimile:	(07) 3365 7031
Telephone:	(07) 3365 4417 (International: +61 7 3365 4417)
		AusCERT personnel answer during Queensland business hours
		which are GMT+10:00 (AEST).
		On call after hours for emergencies.


-----BEGIN PGP SIGNATURE-----
Version: 2.6.3i
Charset: noconv
Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key

iQCVAwUBOlSM6Sh9+71yA2DNAQGSjwQAhQfQWxyNtbg7bU+UX2JqEeGZW5wmuhNM
ohIG4KZHrq3w+BCfM8ZOtAlxrk6j3r8zZDARzBctv1JurBCA4RBZ9HwPsJvmZerh
zgUzzFMVm3wXmhdkywtYYmLy9MiePimsFGKraKKqHQg2zPGBRuumox/oWRb/ohzm
TQrAFlc+fZQ=
=paBD
-----END PGP SIGNATURE-----