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.