Elastic Elasticsearch: CVE-2018-17244: Concurrent Execution using Shared Resource with Improper Synchronization

Elasticsearch Security versions 6.4.0 to 6.4.2 contain an error in the way request headers are applied to requests when using the Active Directory, LDAP, Native, or File realms. A request may receive headers intended for another request if the same username is being authenticated concurrently; when used with run as, this can result in the request running as the incorrect user. This could allow a user to access information that they should not have access to.