Now that CVE-2018-3110 is a hot topic, I think this is a pretty interesting topic to go on.
So, we all know this is consistently one of the components with more CVEs for Oracle Databases. Basically because you can create Java objects in the database (which I think is an abomination :D) and run this code there, usually doing some tricks to escalate privileges to DBA, to PDB, to CDB, to host and other CDBs…
The problem is that (before 18c) OJVM PSU Patches are not RAC Rolling installable. Which means will need a maintenance window to apply fixes for this component. Quite bad, hãn… And if you discover a vulnerability and the PSU window is only in a month or so?
Well, we have a solution 🙂
It is well described in MOS Oracle Recommended Patches — “Oracle JavaVM Component Database PSU and Update” (OJVM PSU and OJVM Update) Patches (Doc ID 1929745.1), under the name “Mitigation Patch”.
It basically consists in install a patch Patch 19721304: SCRIPT TO LOCK DOWN JAVA DEVELOPMENT, which is a Rolling Patch, which allows you to disable any new Java object to be created. This is, so, assuming exploits can be done by creating new java objects on DB (as most of Java CVEs). Also, this patch don’t have any version requirement (after 9i).
Having the patch, however, doesn’t mean you are automatically protected against any vulnerability, but means you can protect yourself temporary by disabling new java objects creation with “exec dbms_java_dev.disable;” anytime.
The Mitigation Patch does not remove Java objects or block any java execution, it only disable the creation of new Java objects, so if the exploit is already planted, it’s not a viable solution. The mitigation patch can be used in any scenario where the PSU or proper JVM fixes cannot be applied at the moment but it’s wanted to prevent against JVM vulnerabilities.
Now, before downloading the patch, first check if it’s not already installed to your home, as it’s part of some Boundle Patches, like “Database Bundle Patch : 126.96.36.199.180417 (27338029)“.
Important Note: The intent is to be like a “workaround” while the PSU is planned. This was not built to be definitive solution. The idea is to just disable new Java objects to be created until the fix is applied on the proper planned maintenance window.
Hope it helps!