[standalone@localhost:9990 /] /subsystem=undertow/configuration=filter/mod-cluster=modcluster:write-attribute(name=ssl-context,value=test
{
    "outcome" => "failed",
    "failure-description" => "WFLYCTL0158: Operation handler failed: java.lang.IllegalStateException: WFLYCTL0365: Capability 'org.wildfly.undertow.mod_cluster_filter.modcluster' is unknown in context 'global'.",
    "rolled-back" => true
}