In Kibana X-Pack security versions prior to 5.4.3 if a Kibana user opens a crafted Kibana URL the result could be a redirect to an improperly initialized Kibana login screen. If the user enters credentials on this screen, the credentials will appear in the URL bar. The credentials could then be viewed by untrusted parties or logged into the Kibana access logs.
With X-Pack installed, Kibana versions before 5.3.1 have an open redirect vulnerability on the login page that would enable an attacker to craft a link that redirects to an arbitrary website.
Kibana versions prior to 5.2.1 configured for SSL client access, file descriptors will fail to be cleaned up after certain requests and will accumulate over time until the process crashes.