Oracle Java Runtime Environment (JRE): code execution flaw under attack

What is affected

Oracle Java Runtime Environment (JRE) is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

A vulnerability in the way Java restricts the permissions of Java applets could allow an attacker to execute commands on a vulnerable system.

What an attacker can do

This is a code execution flaw. It lets an attacker run their own commands or programs on the affected system. In practice that usually means taking it over: installing malware, stealing data or using it to reach other devices on the same network.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

CISA records this vulnerability as known to be used in ransomware campaigns: attackers use it to get in, then encrypt files and demand payment.

What to do

1. Update Oracle Java Runtime Environment (JRE) now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply updates per vendor instructions.

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on May 25, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by June 15, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 97% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.9% of all scored vulnerabilities.

Its CVSS severity score is 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

Multiple vulnerabilities in Oracle Java 7 before Update 11 allow remote attackers to execute arbitrary code by (1) using the public getMBeanInstantiator method in the JmxMBeanServer class to obtain a reference to a private MBeanInstantiator object, then retrieving arbitrary Class references using the findClass method, and (2) using the Reflection API with recursion in a way that bypasses a security check by the java.lang.invoke.MethodHandles.Lookup.checkSecurityManager method due to the inability of the sun.reflect.Reflection.getCallerClass method to skip frames related to the new reflection API, as exploited in the wild in January 2013, as demonstrated by Blackhole and Nuclear Pack, and a different vulnerability than CVE-2012-4681 and CVE-2012-3174. NOTE: some parties have mapped the recursive Reflection API issue to CVE-2012-3174, but CVE-2012-3174 is for a different vulnerability whose details are not public as of 20130114. CVE-2013-0422 covers both the JMX/MBean and Reflection API issues. NOTE: it was originally reported that Java 6 was also vulnerable, but the reporter has retracted this claim, stating that Java 6 is not exploitable because the relevant code is called in a way that does not bypass security checks. NOTE: as of 20130114, a reliable third party has claimed that the findClass/MBeanInstantiator vector was not fixed in Oracle Java 7 Update 11. If there is still a vulnerable condition, then a separate CVE identifier might be created for the unfixed issue.