From
https://issues.apache.org/jira/browse/SOLR-13301:
"ConfigAPI allows to set a jmx.serviceUrl that will create a new JMXConnectorServerFactory and trigger a call with 'bind' operation to a target RMI/LDAP server. A malicious RMI server could respond with arbitrary object that will be deserialized on the Solr side using java's ObjectInputStream, which is considered unsafe. This type of vulnerabilities can be exploited with ysoserial tool. Depending on the target classpath, an attacker can use one of the "gadget chains" to trigger Remote Code Execution on the Solr side."