mailing list archives
RE: NetScreen ScreenOS 2.6 Subject to Trust Interface DoS
From: Alexander Poizner <APoizner () hipinteractive com>
Date: Fri, 1 Feb 2002 12:36:35 -0500
It is a well known problem for many of the firewall appliances
including Sonicwall, Netscreen, PIX etc. The problem is that the traffic on
trusted network interface is partially assumed secure.
If firewall uses port translation for the outgoing connection they
are of course limited by <2^16 ports per IP once all of them are used, you
are in trouble. Of course if the firewall is well designed, it will tell you
in a log that maximum # of connections is reached and it will not allow
connection to management interface until there will be available connection.
Some firewalls of course will just shut down management interface
like did the Sonicwall up until about a year ago. This IS a bug and should
be fixed, however other than that there is not much you can do. Some
firewalls can have multiple IP addresses just for increasing maximum # of
connections. If maximum number of connections specified is exceeded - that
is a problem of system administrator.
Higher end firewalls have some QoS algorithms implemented to protect
you from that condition though. Also in some implementation you might get
away with using NAT for the host that will produce large amount of
connections - but then you got physical limitations of different memory
Systems Security Engineer
HIP Interactive Corp.
(416) 249-7555 x206
From: Chris Lathem [mailto:clathem () skyhawke com]
Sent: Friday, February 01, 2002 10:07
To: bugtraq () securityfocus com
Subject: NetScreen ScreenOS 2.6 Subject to Trust Interface DoS
Problem: NetScreen ScreenOS 2.6.1 subject to Trust
Interface DoS Attack
Company Info: NetScreen Technologies are the
manufacturers of some of the industry's highest
quality VPN and firewall equipment. For more
information please see http://www.netscreen.com.
What's affected: The ScreenOS is the heart of the
NetScreen products. This allows for the firewall
configuration/management. Apparently all versions
before ScreenOS 3.1 are affected. This vulnerability
can only occur from within the "trusted" network, or
from a machine connected to the "trust" interface.
External attempts will not cause any problems/DoS.
Exploit: Someone within the trusted side of the
network can attempt a portscan on an external IP
address. When the scan runs it appears to consume
all of the available sessions. This, in turn, causes a
DoS to the entire trusted interface. The only way I got
my device to recover quickly was to perform a reset.
A recovery might be possible without a reset, but
after about 5 minutes of waiting, mine never
recovered. This exploit may or may not work on your
device. My testing was performed on a NetScreen 5.
The higher-end, more pricier models may take longer
to "eat up" all the available sessions, thus taking
longer for a DoS to occur.
I have contacted NetScreen in regards to the issue. I
received a response back that the problem is a
known issue. It has been addressed in ScreenOS
3.1. An update to ScreenOS 3.1 is available for
anyone with a NetScreen 200 or 500. For all other
models, the update to ScreenOS 3.1 will be available
on April 1, 2002.
I'd love to hear if anyone else has noticed this, or if
other models are affected by this issue.
chris () lathemonline com