Description
GeoServer WMS allows an unauthenticated attacker to send arbitrary requests to perform lookups on the internal network which is otherwise not accessible externally. An attacker may use this feature to perform SSRF (server-side request forgery) attacks on the server.
Remediation
Upgrade to the latest version of GeoServer
References
WPS Server Side Request Forgery
Unauthenticated Server Side Request Forgery & CRLF injection in Geoserver WMS