Original release date: August 10, 2000<BR>
Source: CERT/CC<BR>

<P>A complete revision history is at the end of this file.

<A NAME="affected">
<H3>Systems Affected</H3>

<LI>Systems running Netscape Communicator version 4.04 through 4.74
with Java enabled. Netscape 6 is unaffected by this problem.

<A NAME="overview">

<P>Netscape Communicator and Navigator ship with Java classes that
allow an unsigned Java applet to access local and remote resources in
violation of the security policies for applets.

<A NAME="description">
<H2>I. Description</H2>

<p>Failures in the netscape.net package permit a Java applet to read
files from the local file system by opening a connection to a URL
using the "file" protocol. For example, by opening a connection to
"file:///C:/somefile.txt" an intruder can read the contents of that

<p>Additionally, it is possible to use this technique to open
connections to resources using other types of protocols; that is, it
is possible to open a connection to "http," "https," "ftp," and other
types of URLs using this vulnerability.

<p>By then using ordinary techniques, a malicious Java applet that
exploits this vulnerability could subsequently send the contents of
the file (or other resource) to the web server from which the applet

<p>An exploit using this technique causes the victim to
establish a connection to the malicious web server (as opposed to the
intruder establishing a connection to the victim). Thus typical
firewall configurations fail to stop an attack of this type.

<P>A tool written by Dan Brumleve dubbed "Brown Orifice" demonstrates
this vulnerability.  Brown Orifice implements an HTTP server (web
server) as a Java applet and listens for connections to the victim's
machine. In conjunction with the Netscape vulnerability, Brown Orifice
essentially turns a web browser into a web server and allows any
machine on the Internet to browse the victim's local file
system. Typical firewall configurations stop this type of attack, but
as noted above, they do not stop simple variations of this attack.

<p>This vulnerability is the result of an implementation error in the
JRE that comes with the Netscape brower, not an architectural problem
in the Java security model.

<p>This problem has been widely discussed in various forums on the
Internet. More information is available at <P>

<dd><A HREF="http://www.securityfocus.com/bid/1546">http://www.securityfocus.com/bid/1546</a></dd>


(Note that this site contains a demonstration of the vulnerability
which could expose your files to intruders.)


<p>As of the writing of this document, we have not received any
reports indicating exploitation of this vulnerability outside of the
context of obtaining it from the Brown Orifice web site. Note that
running Brown Orifice allows anyone, not just the administrators of
the Brown Orifice web site, to read files on your system. The Brown
Orifice web site publishes the IP address of systems running Brown
Orifice, and we have received reports of third parties attempting to
read files from a system identified on the Brown Orifice web
site. Furthermore, if you have extended any file-reading privileges to
anyone who has run Brown Orifice, your files can be read by anyone on
the Internet (subject to controls imposed by your router and

<A NAME="impact">
<H2>II. Impact</H2>

Intruders who can entice you into running a malicious Java applet can
read any file that you can read on your local or network file
system. Additionally, the contents of URLs located behind a firewall
can be exposed.


<A NAME="solution">
<H2>III. Solution</H2>

<P>Organizations should weigh the risks presented by this
vulnerability against their need to run Java applets. At the present
time, an effective solution is to disable Java in Netscape.
Historically, vulnerabilities of this type have <i>not</i> been widely
exploited; however this is not an indication that they can't be, or that
targeted attacks are not effective and possible. 

<p>For organizations that have a need to run Java applets under their
own control (that is, in situations where the HTML page referencing
the applet is under their control), an alternate solution is to
install a Java Runtime Environment Plugin available from Sun
Microsystems. More information and pointers to downloadable software
is available at


<p>To use this plugin effectively requires the use of a tool to
convert HTML pages to use a different tag. Information about Sun's
HTML Converter Software is also available on <A
page</a>. This tool will rewrite HTML pages so that applets referenced
in the page will run in the JRE provided by the plugin.

<p>To achieve protection from the resource reading vulnerability using
this tool requires you to disable Java in the Netscape browser. The
HTML Converter software will modify HTML pages to use an
&lt;EMBED&gt; tag instead of an &lt;APPLET&gt;. The JRE plugin
software recognizes the &lt;EMBED&gt; tag, and applets will then run
within the new JRE plugin, instead of the default JRE provided by

<P><A HREF="#vendors">Appendix A</a> contains information provided by
vendors for this advisory. We will update the appendix as we receive
more information.  If you do not see your vendor's name, the CERT/CC
did not hear from that vendor. Please contact your vendor


<A NAME="vendors">
<H2>Appendix A. Vendor Information</H2>

<H4>AOL Corporate Communications</H4> 

<p>Netscape takes all security issues very seriously, and we are
working to quickly evaluate and address this concern.  If the reports
are accurate, we plan to make a patch available, but in the interim,
users can protect themselves by simply turning off Java.

<p>Users can also visit <A HREF="http://www.netscape.com/security">http://www.netscape.com/security</a> to get the
mostup to date information on a patch, and its availability.

<A NAME="Netscape and Sun">
<H4>Sun Microsystems and Netscape</H4> 

<p>Sun is working with Netscape to deliver a new version of Navigator
and Communicator that will fix this problem.

<A NAME="Microsoft">

<p>Brown Orifice does not exploit any vulnerabilities in
Microsoft Products.


<P>The CERT Coordination Center thanks Elias Levy, CTO of
SecurityFocus.com, and Sun Microsystems and AOL/Netscape for their
input and assistance in the construction of this advisory.


<P>Author: <a
href="mailto:cert@cert.org?subject=CA-2000-15%20Feedback">Shawn Hernan</a>


<!--#include virtual="/include/footer_nocopyright.html" -->

<P>Copyright 2000 Carnegie Mellon University</P>

<P>Revision History

August 10, 2000:  Initial release