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Researchers have discovered a flaw in the latest version of Oracle's Java runtime environment that attackers can exploit to remotely execute malicious code on end user machines.

The bug in the Java Web Start component has been confirmed exploitable on all recent versions of Windows by Tavis Ormandy, a security researcher who prefers his employer not be named. Fellow researcher Ruben Santamarta of Spain-based security firm Wintercore, said a related flaw potentially affects Linux users as well.

Both researchers criticized the reaction.

"The method by which Java Web Start support has been added to the JRE is not less than a deliberately embedded backdoor (I really don't think so) or a flagrant case of extreme negligence (+1)," Santamarta wrote here. "It's even more incredible that Sun didn't assess the real risk of this flaw after Tavis reported it to them."

The vulnerable Windows components uncovered by Ormandy include an ActiveX control known as Java Deployment Toolkit and a Firefox plugin known as NPAPI, which are designed to make it easy for Java developers to distribute their applications to end users. These components accept commands embedded in web pages or URLs without proper scrutiny and then pass them to another component for execution.

A hidden command-line parameter supported by Java can trigger the bug on Linux machines as well, Santamarta told The Register. He said he was in the process of testing whether the flaw can be exploited to remotely execute code.

Ormandy warned that it won't be easy for users to protect themselves from the vulnerability short of installing a patch. Merely disabling ActiveX or Firefox plugins isn't enough because the toolkit is installed separately from Java. That means the only temporary fixes are browser specific for IE and Firefox and involve setting killbits or employing file system access control list features. (More about that here).

Of course, there's another mitigation that was tweeted Friday by security researcher Alex Sotirov that's looking more and more viable.

"I uninstalled Java more than a year ago and haven't had a single problem with any website," he wrote. "Why are people still running Java in the browser?"

Good question. ®

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