An error was found in the permission model used by X-Pack Alerting 5.0.0 to 5.6.0 whereby users mapped to certain built-in roles could create a watch that results in that user gaining elevated privileges.

Elastic X-Pack Security versions 5.0.0 to 5.4.0 contain a privilege escalation bug in the run_as functionality. This bug prevents transitioning into the specified user specified in a run_as request. If a role has been created using a template that contains the _user properties, the behavior of run_as will be incorrect. Additionally if the run_as user specified does not exist, the transition will not happen.

The join_session_keyring function in security/keys/process_keys.c in the Linux kernel before 4.4.1 mishandles object references in a certain error case, which allows local users to gain privileges or cause a denial of service (integer overflow and use-after-free) via crafted keyctl commands.