I faced with this error message on our 11g 2 Node  RAC database.

We have been enabled block change tracking to can take Inceremental backup. After this,  Instance 2 has been  reebot from our 2 node RAC system with ORA-00600: internal error code, arguments: [krccaub_2], [505], [40], [], [], [], [], [], [], [], [], [] error!

We found some related information at metalink but We decide its better to confirm this issue with Oracle Support.

This issue is related to bug 7312717 which is detail available at below link:

Bug 7312717 [http://bug.oraclecorp.com/pls/bug/webbug_edit.edit_info_top?rptno=7312717]

The workaround is to disable block change tracking:

To disable block change tracking:

1. Start SQL*Plus and connect to a target database with administrator privileges.
2. Ensure that the target database is mounted or open.
3. Disable block change tracking.

Execute the following ALTER DATABASE statement:

ALTER DATABASE DISABLE BLOCK CHANGE TRACKING;

If you cant disable block change tracking than you need to apply one of a patch to your database.

Reference:

ORA-600 [krccaub_2] can occur with block change tracking [ID 7312717.8]
ORA-600 [krccaub_2] Locator is not for the correct file [ID 1268896.1]