Remote Code Execution (RCE) through the REST API in Splunk Enterprise

Summary

In Splunk Enterprise versions below 10.4.2, 10.2.6, 10.0.9, and 9.4.14, a user who does not hold the "admin" or "power" Splunk roles could perform Remote Code Execution (RCE) by uploading a malicious knowledge bundle and causing it to be used by distributed search, which can allow for access to all relevant data and affect system integrity and availability. The vulnerability is possible because the Representational State Transfer (REST) API endpoint for knowledge bundle upload does not require the high-privilege capability edit_dist_peer, and distributed search accepts caller-supplied knowledge bundle selections from users who do not hold that capability. For more information see What search heads send to search peers (https://help.splunk.com/en/splunk-enterprise/administer/distributed-search/9.2/knowledge-bundle-replication/what-search-heads-send-to-search-peers), About configuring role-based user access (https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/9.0/manage-splunk-platform-users-and-roles/about-configuring-role-based-user-access), Define roles on the Splunk platform with capabilities (https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/9.1/manage-splunk-platform-users-and-roles/define-roles-on-the-splunk-platform-with-capabilities), and Using the REST API reference (https://help.splunk.com/en/splunk-enterprise/rest-api-reference/10.4/introduction/using-the-rest-api-reference) in the Splunk documentation.