Original issue date: April 22, 1993<BR>
Last revised: September 19, 1997<BR>
Attached copyright statement

<P>A complete revision history is at the end of this file.

<P>The CERT Coordination Center 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 &quot;no ip source-route&quot;
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.

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

<P>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: 
	<A HREF=mailto:tac@cisco.com>tac@cisco.com</A> 
)
for more information.

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

<P>
<PRE>
    Release  (Update)
      8.3      (8)
      9.0      (5)
      9.1      (4)
      9.17     (3)
</PRE>

<P>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.

<P><HR>

<P>
<H2>I. Description</H2>

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

<P><PRE>
     no ip source-route
</PRE>

<P>may allow traffic which should be suppressed.

<P>
<H2>II. Impact</H2>

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

<P>
<H2>III. Solution</H2>

<P>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. 

<P>Customers who have questions should contact the Cisco Technical
Assistance Center at 800-553-2447 for assistance. Internet:
<A HREF=mailto:tac@cisco.com>tac@cisco.com</A> 

<P><HR>
The CERT Coordination Center wishes to thank Cisco Systems for responding
to this problem.

<!--#include virtual="/include/footer_nocopyright.html" -->
<P>Copyright 1993 Carnegie Mellon University.</P>

<HR>

Revision History
<PRE>
September 19,1997  Attached Copyright Statement
</PRE>