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Title: Juniper Networks NetScreen Advisory 59110
Date: 30 August 2004
Version: 5


Impact:
Remote crash of ScreenOS via the SSHv1 service


Affected Products:
    Juniper Networks NetScreen firewalls with SSHv1 enabled


Unaffected Products:
    Juniper Networks NetScreen firewalls with SSH disabled or SSHv2 enabled
    Juniper Networks NetScreen NS-10


Max Risk: High


Summary:
The Juniper Networks NetScreen firewall SSHv1 service implementation has
a bug which allows an attacker to crash ScreenOS.


Details:
A malicious person who can connect to the SSHv1 service on a Juniper
Networks Netscreen firewall (other then the NS-10) can crash the device before
having to authenticate.  Upon execution of the attack, the firewall will
reboot or hang, which will prevent traffic to flow through the device.


Recommended Actions:
Customers have a number of choices to mitigate the attack:

Option 1:  Upgrade the firewall to one of the following versions of
ScreenOS:

Version                         Availability 
5.0.0r8 (except ISG2000)            Now
5.0.0r8 (ISG2000)               Aug 25, 2004
5.0.0r8.1                           Now
4.0.0r13 (NS100)                    Now
4.0.3r8                             Now
4.0.0-Dial2r8                       Now
4.0.1-SBRr7                         Now
4.0.1-MCASTr3                       Now
3.0.3r9                             Now 

Option 2:  Disable SSHv1 and manage the device through other means (such
as HTTPS).

Option 3:  Configure the firewall to only accept connections from
trusted IP addresses.  Additionally, enabling IP Spoof protection will
add an additional layer of security.


Patch Availability:
Juniper Networks currently has updated versions of ScreenOS available
for immediate download.


How to get ScreenOS:
Customers with a valid product warranty or a support contract may
download the software from the Juniper Networks CSC web portal:
http://www.juniper.net/support/

For all other customers, including those with expired support contracts,
please call your regional Juniper Networks TAC (JTAC) center.  To get a
listing of JTAC phone numbers, please sign up for a CSC account at:
http://www.juniper.net/entitlement/setupAccountInfo.do

Select option 2 from the telephone menu and be sure to select the
correct product from the phone tree.  Once connected with an engineer
state that you are calling in regards to a Security Advisory and provide
the title of this notice as evidence of your entitlement to the
specified release.

Please note that customers with expired support contracts will be
provided only with the software update for the version of software that
they are currently using, when that version becomes available.

As with any new software installation, Juniper Networks customers
planning to upgrade to any version of ScreenOS should carefully read the
release notes and other relevant documentation before beginning any
upgrade.


Juniper Networks would like to thank Mark Ellzey Thomas of NaviSite for
discovering this issue and working with us.


If you wish to verify the validity of this Security Advisory, the public
PGP key can be accessed at:
http://www.juniper.net/support/security/


Changes in Version 2:
. Corrected errors in list of ScreenOS with the fix
. Corrected Security Alert ID.  Old ID (59147) was incorrect.

Changes in Version 3:
. Corrected another error in the list of ScreenOS with the fix.

Changes in Version 4:
. Corrected another error in the list of ScreenOS with the fix.

Changes in Version 5:
. Updated the advisory to show that the NS-10 is not vulnerable.
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