Server-Side Request Forgery (SSRF) through the Report Notification REST API in Splunk Secure Gateway

In Splunk Enterprise versions below 10.4.2, 10.2.6, 10.0.9, and 9.4.14, and Splunk Secure Gateway versions below 3.10.9, 3.9.23, and 3.8.70, a user who does not hold the "admin" or "power" Splunk roles could use crafted report notification data to cause Splunk Secure Gateway to send a request to the Splunk Enterprise Representational State Transfer (REST) API using a system-level session token and modify the Splunk platform configuration. The user could then obtain a session token without a password and use it to access all relevant data and affect system integrity. The vulnerability is possible because Splunk Secure Gateway does not validate decoded report notification identifiers before using them to construct requests to the Splunk Enterprise REST API.