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Vulnerability plagues Java implementations

Apr 05, 1999, 14:24 (4 Talkback[s])
(Other stories by Gary McGraw)

Gary McGraw posted to BUGTRAQ:

Hi all,

Karsten Sohr at the University of Marburg in Germany (email sohr@mathematik.uni-marburg.de) has discovered a very serious security flaw in several current versions of the Java Virtual Machine, including Sun's JDK 1.1 and Java 2 (a.k.a. JDK 1.2), and Netscape's Navigator 4.x. (Microsoft's latest JVM is not vulnerable to this attack.) The flaw allows an attacker to create a booby-trapped Web page, so that when a victim views the page, the attacker seizes control of the victim's machine and can do whatever he wants, including reading and deleting files, and snooping on any data and activities on the victim's machine.

The flaw is in the "byte code verifier" component of the JVM. Under some circumstances the verifier fails to check all of the code that is loaded into the JVM. Exploiting the flaw allows the attacker to run code that has not been verified. This code can set up a type confusion attack (see our book "Securing Java" for details http://www.securingjava.com) which leads to a full-blown security breach.

We have verified that the flaw exists and is serious. Attack code (in both applet and application form) has been developed in the lab to exploit the flaw. Sun and Netscape have been notified about the flaw and they are working on a fix.

The attack we developed in the lab worked against the following platforms:
JDK 1.1.5 (Solaris)
JDK 1.2beta4 (Solaris)
JDK 1.1.6 (Solaris)
JDK 1.1.7 (FreeBSD)
JDK 1.2 (NT)
JDK 1.1.6 (NT)
Symantec Visual Cafe Version 3
Netscape 4.5 (FreeBSD)
Netscape 4.5 (NT)
Netscape 4.05 (NT)
Netscape 4.02 (Solaris)
Netscape 4.07 (Linux)

The attack did not work against:
Microsoft Visual J++ 6.0

Kudos to Viren Shah at RST for extensive platform testing. Thanks for your interest in mobile code security.

Dr. Gary McGraw                      Prof. Edward W. Felten
Reliable Software Technologies       Secure Internet Programming Lab
gem@rstcorp.com                      Dept. of Computer Science
                                     Princeton University
http://www.securingjava.com          felten@cs.princeton.edu