'Critical' Java Flaw Bugs Researchers

Sun patches some versions of Java - another patch, for consumers, is due this week

A serious Java vulnerability just patched by Sun Microsystems may still leave many Java users at risk, security experts say.

The stack buffer overflow bug in Java, the WebStart utility in the Java Runtime Environment, could be used by an attacker to insert a bot agent, rootkit, or backdoor malware on the victim's machine. A user would get infected either by clicking on a malicious link, or by unknowingly getting redirected to an infected Website. (The malware is contained in Java JNLP files.)

"Anyone with Java installed on Windows is automatically configured to load JNLP files without prompting," notes HD Moore, creator of Metasploit. "So it's pretty serious since it affects everyone [who has] Java installed."

Sun recently patched JRE 5 and the Java 6 developer version, but hasn't yet pushed a patch to consumer users' version 6, which it plans to do this week. The bug's danger at this point to users may be more a function of the patch process itself, according to security experts. "Most companies' patch management software is not configured to patch Java," says Marc Maiffret, eEye's CTO and chief hacking officer. "To make matters worse, Sun has such a horrible update process -- they released patches for this flaw a couple of weeks ago, and then more patches for a different version today. Which means if people were reverse-engineering the patch a few weeks ago, now they have a head start on the good guys."

A Sun spokesperson declined to comment on eEye's criticism of its patch process, but says the consumer version of the Java 6 patch is still being tested and should be available this week. Sun first issued a patch for the bug on June 28, for JRE 5, and then on July 2, it released a patch for Java 6 developers.

eEye, which discovered the bug over six months ago, has labeled the bug as "critical."

Still, neither Maiffret nor Metasploit's Moore were aware of any exploits in the wild based on this bug. eEye recommends that Java users immediately install the patches, which are available from Sun at for JRE 5 Update 12 and at for JRE 6 Update 2.

— Kelly Jackson Higgins, Senior Editor, Dark Reading

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