-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

===============================================================================
>>                                                      CERT-NL, 01-Mar-2000 <<
>> All CERT-NL information has been moved to http://cert.surfnet.nl.  Links  <<
>> to CERT-NL information contained in this advisory are therefore outdated. <<
>>                                                                           <<
>> CERT-NL also has stopped the CERT-CC-Mirror service.  Due to this the     <<
>> links to the CERT-CC mirror are obsolete. Visit the CERT-CC site for the  <<
>> complete CERT-CC advisory texts:                     http://www.cert.org  <<
===============================================================================
===============================================================================
Security Advisory                                                       CERT-NL
===============================================================================
Author/Source : CERT-NL (Erik-Jan Bos)                      Index  :    S-93-12
Distribution  : World                                       Page   :          1
Classification: External                                    Version:      Final
Subject       : Cisco Router Packet Handling Vulnerability  Date   :  23-Apr-93
===============================================================================

CERT-NL has received information indicating that under some
circumstances Cisco routers will pass IP source routed packets which
should have been denied. Routers which do not use the "no ip
source-route" command are not affected. This vulnerability applies to
all models of Cisco routers. This problem occurs with the following
releases of software: 8.2, 8.3, 9.0, 9.1 and 9.17.

Cisco Systems and CERT-NL recommend that sites using Cisco routers to
provide firewall protection take action to eliminate this vulnerability
from their networks.

This security issue is fixed in Cisco software releases 8.3(7.2),
9.0(5), 9.1(4) 9.17(2.1) and in all later releases. Customers who are
using software release 8.2 must upgrade to a later release and should
contact Cisco's Technical Assistance Center (TAC) at 800-553-2447
(Internet: tac@cisco.com) for more information.

Cisco recommends that customers whose routers may be affected by this
vulnerability upgrade their software to the following versions:

      Release (Update)  
        8.3     (8)
        9.0     (5)
        9.1     (4)
        9.17    (3)

These releases are available on Cisco's Customer Information On-Line
(CIO) service for those customers having a maintenance contract. Other
customers may obtain these releases through Cisco's Technical
Assistance Center or by contacting their local Cisco distributor.

- -----------------------------------------------------------------------------

I.   Description

     A vulnerability exists in Cisco routers such that a router which 
     is configured to suppress source routed packets with the following
     command:

              no ip source-route

     may allow traffic which should be suppressed.

II.  Impact

     This vulnerability can allow unauthorized traffic to pass through
     the router/gateway.

III. Solution

     Cisco recommends that affected customers upgrade to a later version. 
     Customers who cannot upgrade immediately may be able use access lists 
     to prevent unauthorized traffic. 

     Customers who have questions should contact the Cisco Technical
     Assistance Center at 800-553-2447 for assistance. Internet:
     tac@cisco.com

- ---------------------------------------------------------------------------
The CERT Coordination Center wishes to thank Cisco Systems for responding
to this problem.
- ---------------------------------------------------------------------------


==============================================================================
CERT-NL is the Computer Emergency Response Team for SURFnet customers. SURFnet
is the Dutch network for educational, research and related institutes. CERT-NL
is a member of the Forum of Incident Response and Security Teams (FIRST).

All CERT-NL material is available under:
  http://cert.surfnet.nl/

In case of computer or network security problems please contact your local
CERT/security-team or CERT-NL  (if your institute is NOT a SURFnet customer
please address the appropriate (local) CERT/security-team).

CERT-NL is one/two hour(s) ahead of UTC (GMT) in winter/summer,
i.e. UTC+0100 in winter and UTC+0200 in summer (DST).

   Email:     cert-nl@surfnet.nl     ATTENDED REGULARLY ALL DAYS
   Phone:     +31 302 305 305        BUSINESS HOURS ONLY
   Fax:       +31 302 305 329        BUSINESS HOURS ONLY
   Snailmail: SURFnet bv
              Attn. CERT-NL
              P.O. Box 19035
              NL - 3501 DA  UTRECHT
              The Netherlands

NOODGEVALLEN:    06 22 92 35 64      ALTIJD BEREIKBAAR
EMERGENCIES : +31 6 22 92 35 64      ATTENDED AT ALL TIMES
CERT-NL'S EMERGENCY PHONENUMBER IS ONLY TO BE USED IN CASE OF EMERGENCIES:
THE SURFNET HELPDESK OPERATING THE EMERGENCY NUMBER HAS A *FIXED*
PROCEDURE FOR DEALING WITH YOUR ALERT AND WILL IN REGULAR CASES RELAY IT
TO CERT-NL IN AN APPROPRIATE MANNER. CERT-NL WILL THEN CONTACT YOU.
===============================================================================

-----BEGIN PGP SIGNATURE-----
Version: PGP 6.5.1i

iQA/AwUBOL6WBTSYjBqwfc9jEQL3AgCg8hauVaD8S1QCnk0PdZhTSoc/9oEAoIlb
wJGNNviFHNqzkU4VnEbFE53Y
=cVhL
-----END PGP SIGNATURE-----