The Splunk Enterprise REST API allows enumeration of usernames via the lockout error message. The potential vulnerability impacts Splunk Enterprise instances before 8.1.7 when configured to repress verbose login errors.
See Authentication.conf for more information on verboseLoginFailMsg setting. If the Splunk Enterprise instance uses the default verboseLoginFailMsg or sets verboseLoginFailMsg to true, it is not impacted. However, we strongly recommend setting verboseLoginFailMsg to false.
The vulnerability does not allow the enumeration of users with the default admin role or never_lockout capability. See Roles and capabilities for more formation on never_lockout.
Upgrade Splunk Enterprise versions to 8.1.7 or later.