A new Java zero-day vulnerability is being exploited by attackers, and until it is patched everyone should disable Java in their browser.
The vulnerability targets browsers that have the latest version of the Java plugin installed – Java v1.6 Update 41 and Java v1.7 Update 15 – malware researchers FireEye reported on Thursday.
It has been used to attack multiple customers, FireEye said.
"We urge users to disable Java in your browser until a patch has been released; alternatively, set your Java security settings to 'High' and do not execute any unknown Java applets outside of your organization," the researchers wrote.
The exploit attempts to download a McRAT command-and-control executable onto the user's computer. McRAT ensures its persistence by writing a copy of itself as a DLL and making registry modifications.
Fortunately for web users the world over, the exploit "is not very reliable", the researchers write. In most cases, the payload fails to execute and leads to a JVM crash.
Oracle has assigned CVE-2013-1493 to the vulnerability, but at the time of writing had not responded to requests for further information or issued a patch.
This vulnerability follows a widespread zero-day Java attack against large tech companies Apple, Facebook, Microsoft, Twitter, and others in January.
Oracle issued a Java Critical Patch Update on February 1 in what now seems to be a response to these attacks, but the patch wasn't watertight, and the database giant was forced to issue another update on February 19. It seems that fix was not sufficient. ®