Systems IOS is vulnerable to a denial-of-service attack using ICMP
Redirect messages.
When flooded with ICMP redirect messages, the IOS uses up all its memory
to store the new host routes. The device is then unable to perform
operations that need additional memory such as receiving routing updates
and accepting inbound telnet(1) connections.
DETAILS
Known vulnerable combinations:
* 1005 with IOS 11.0(18)
* Cisco 1603 with IOS 11.3(11b)
* Cisco 1603 with IOS 12.0(3)
* Cisco 2503 with IOS 11.0(22a)
* Cisco 2503 with IOS 11.1(24a)
Known to be not vulnerable:
* Cisco 1603 with IOS 12.1(11)
* Cisco 1603 with IOS 12.2(5)
* Cisco 2503 with IOS 11.2(26a)
* Cisco 2503 with IOS 11.3(11b)
* Cisco 2503 with IOS 12.0(19)
Description:
ICMP redirect messages are used in IP networks to inform a sending device
about inefficient routing. Cisco IOS software stores redirect messages it
receives in memory for further consultation. They do not become part of
the normal routing table.
When generating ICMP redirect messages with random IP addresses in the
"offending packet" section of the ICMP frame, IOS will include this IP
address in its ICMP redirection table. In the vulnerable versions of IOS,
this table has no size limit. Later versions of IOS enforce a limit of
16000 redirects and therefore limit the amount of used memory to
approximately 1.16MB.
Some device/IOS combinations tested were unable to perform normal IP
routing for a limited time, but most combinations continued to function as
a router. In some cases, even access to the console was denied because of
low memory.
According to
recover after 4 hours since the redirect table entries time out. However,
vulnerable versions tested did not recover.
Vendor status:
11/16/2001 to 05/05/2002 Contacted Cisco 8 times over past 6 months
concerning status.
05/07/2002 Gaus says Cisco developers assigned a low priority to the bug.
05/11/2002 Provide a copy of this file to Cisco prior to publication.
05/20/2002 Final corrections by Cisco included.
05/21/2002 Info from Cisco: Fix available shortly.
Example:
To generate random ICMP redirect messages, a sender tool is available at
<>
, which has to be linked with
the IRPAS packet library.
box# cd /where/irpas/is
box# make libpackets.a
linuxbox# gcc -o icmp_redflod -I. -L. icmp_redflod.c -lpackets
linuxbox# ./icmp_redflod -i eth0 -D
On high bandwidth networks, the command line switch -w0 can be used to
increase the sending rate.
Solution:
Filter inbound ICMP redirect messages or update your IOS to either a not
vulnerable release or a fixed version when these become available.
Exploit code:
/* ICMP redirect flooder
*
* FX
* Phenoelit ()
* (c) 2k++
*
* $Id: icmp_redflod.c,v 1.3 2002/05/11 14:59:06 fx Exp fx $
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include 【责编:admin】
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