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Untrusted Java applet can connect to localhost
From: NGSSoftware Insight Security Research <nisr () ngssoftware com>
Date: Mon, 29 Oct 2007 14:20:22 -0700 (Pacific Daylight Time)

Note: This advisory should have been published several months ago;
apologies for the delay -- John Heasman

=======
Summary
=======
Name: Untrusted Java applet can connect to localhost
Release Date: 29 October 2007
Reference: NGS00443
Discover: John Heasman <john () ngssoftware com>
Vendor: Sun Microsystems
Systems Affected: JDK and JRE 6 Update 1 and earlier, JDK and JRE 5.0
Update 11 and earlier, SDK and JRE 1.4.2_14 and earlier
Risk: Medium
Status: Published

========
TimeLine
========
Discovered:  1 October 2006
Released:  2 October 2006
Approved:  7 October 2006
Reported:  1 November 2006
Fixed: 18 July 2007
Published: 29 October 2007

===========
Description
===========
The Java browser plugin shipped with versions of the JRE and JDK
listed above, contains a vulnerability that allows an
untrusted applet to violate the network access restrictions placed on it
by the Java sandbox in order to connect to the local host.  This permits a
malicious website to host an applet that is capable of port scanning the
local system and exploiting vulnerable network services (e.g. unpatched
vulnerabilities in MSRPC etc.)

=================
Technical Details
=================
The Java browser plugin allows applets to be loaded from a remote location
most typically over HTTP/HTTPs but also over a number of other supported
protocols including an undocumented protocol scheme "verbatim".  Untrusted
applets are subject to network access restrictions documented at
http://java.sun.com/sfaq/:

"Applets are not allowed to open network connections to any computer,
except for the host that provided the .class files. This is either the
host where the html page came from, or the host specified in the codebase
parameter in the applet tag, with codebase taking precendence."

By specifying a codebase URI prefixed by "verbatim:" it is possible to
load an applet from a remote location but have the browser plugin believe
it has been loaded from the local host.  This allows an untrusted applet
to connect to and attempt to exploit network services running on the local
host.  It should be noted that unlike binary sockets in Flash 9, an applet
can connect to any port, not just those greater than 1024.

At the time of reporting this issue, NGS provided Sun with a demonstration
applet that exploited MS06-040 ("Vulnerability in Server Service could
allow remote code execution") on a vulnerable XP SP1 system.

===============
Fix Information
===============
This issue is addressed in the following releases (for Windows, Solaris,
and Linux):

JDK and JRE 6 Update 2 or later
JDK and JRE 5.0 Update 12 or later
SDK and JRE 1.4.2_15 or later

Further information is available at
http://sunsolve.sun.com/search/document.do?assetkey=1-26-102995-1


NGSSoftware Insight Security Research
http://www.ngssoftware.com/
http://www.databasesecurity.com/
http://www.nextgenss.com/
+44(0)208 401 0070

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