In Splunk Enterprise versions below 10.4.2, 10.2.6, 10.0.9, and 9.4.14, an unauthenticated user who has access to a trusted distributed search private key could forge an administrative session token, access all relevant data, affect system integrity, and disrupt service availability. The vulnerability is possible because the distributed search authentication token endpoint does not require a signed request to identify a configured search peer, allowing the request to fall back to shared local key material. For more information see About distributed search (https://help.splunk.com/en/splunk-enterprise/administer/distributed-search/10.4/overview-of-distributed-search/about-distributed-search) and authentication.conf (https://help.splunk.com/en/splunk-enterprise/administer/admin-manual/10.4/configuration-file-reference/10.4.2-configuration-file-reference/authentication.conf) in Splunk documentation.
Turn off legacy distributed search token fallback by setting strictPeerNameValidation = true in the authentication.conf configuration file if you do not use distributed search peers that omit peername. Restart Splunk Enterprise on every node in the distributed environment after applying the setting. For more information see authentication.conf in the Splunk documentation.
Upgrade Splunk Enterprise to versions 10.4.2, 10.2.6, 10.0.9, and 9.4.14, or higher.
Set strictPeerNameValidation = true in authentication.conf on every distributed node, then restart Splunk Enterprise.