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NetWare Screensaver Authentication Bypass From The Local Console
From: Adam Gray <agray () novacoast com>
Date: Sun, 12 Dec 2004 17:24:10 -0800

Novacoast Security Advisory 
Novell Netware 5/5.1/6.0/6.5 Vulnerability 


Synopsis: 
Novacoast has discovered a vulnerability in the Novell NetWare Operating
System screen saver software. The vulnerability allows a local attacker
to bypass authentication and access the system console. 


Description: 
The Novell Operating System uses the screen saver nlm with lock enabled
to protect access to the console. When the screen saver is locked only a
user in the e-directory tree with supervisor rights to the server object
has the ability to unlock it. It is possible to bypass this
authentication scheme by entering the debugger within NetWare while the
screensaver is running, kill the screensaver process, and resume the
operating system without the screen saver or the access control still
running.

Affected Version: 
Novell NetWare 5.1
Novell Netware 6
Novell NetWare 6.5

Exploit: 
with the screensaver nlm running and in enable lock mode press alt shift
shift esc. Find the screen saver process in memory. Kill it using the
debugger. If you are not sure how to use the NetWare debugger then just
kill the server with the q key and restart it without the autoexec.ncf
running (server -na) edit the autoexec.ncf to keep the screensaver from
running in the future and restart the server normally. The screen saver
will not start again.

Recommended Solution: 
Install the Bordermanager ICSA Compliance kit
        They put the screensaver fix into that patch
        

Status: 
This bug has been submitted to, acknowledged by, and a fix has been
created and included with the Bordermanager ICSA Compliance toolkit.

Additional information can be found at the following location: 
http://support.novell.com/cgi-bin/search/searchtid.cgi?/2969741.htm


Disclaimer: 
Novacoast accepts no liability or responsibility for the 
content of this report, or for the consequences of any 
actions taken on the basis of the information provided 
within. Dissemination of this information is granted 
provided it is presented in its entirety. Modifications 
may not be made without the explicit permission of 
Novacoast. 


Adam Gray 
CTO 
Novacoast, Inc. 
agray_at_novacoast.com 
http://www.novacoast.com 

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