diff -urp libvirt-5.1.0.orig/src/qemu/qemu_command.c libvirt-5.1.0/src/qemu/qemu_command.c
--- libvirt-5.1.0.orig/src/qemu/qemu_command.c	2019-03-23 11:41:18.269000000 +0100
+++ libvirt-5.1.0/src/qemu/qemu_command.c	2019-03-23 11:41:44.602000000 +0100
@@ -8155,6 +8155,10 @@ qemuBuildGraphicsVNCCommandLine(virQEMUD
             virCommandAddEnvPair(cmd, "SASL_CONF_PATH", cfg->vncSASLdir);
 
         /* TODO: Support ACLs later */
+
+        if (cfg->vncACL)
+           virBufferAddLit(&opt, ",acl");
+
     }
 
     virCommandAddArg(cmd, "-vnc");
diff -urp libvirt-5.1.0.orig/src/qemu/qemu.conf libvirt-5.1.0/src/qemu/qemu.conf
--- libvirt-5.1.0.orig/src/qemu/qemu.conf	2019-03-23 11:41:18.271000000 +0100
+++ libvirt-5.1.0/src/qemu/qemu.conf	2019-03-23 11:41:44.602000000 +0100
@@ -141,6 +141,15 @@
 #vnc_sasl = 1
 
 
+# Enable the VNC access control lists. When switched on this will
+# initially block all vnc users from accessing the vnc server. To
+# add and remove ids from the ACLs you will need to send the appropriate
+# commands to the qemu monitor as required by your particular version of
+# QEMU. See the QEMU documentation for more details.
+# 
+# vnc_acl = 1
+
+
 # The default SASL configuration file is located in /etc/sasl/
 # When running libvirtd unprivileged, it may be desirable to
 # override the configs in this location. Set this parameter to
diff -urp libvirt-5.1.0.orig/src/qemu/qemu_conf.c libvirt-5.1.0/src/qemu/qemu_conf.c
--- libvirt-5.1.0.orig/src/qemu/qemu_conf.c	2019-03-23 11:41:18.270000000 +0100
+++ libvirt-5.1.0/src/qemu/qemu_conf.c	2019-03-23 11:47:01.904000000 +0100
@@ -471,6 +471,8 @@ virQEMUDriverConfigLoadVNCEntry(virQEMUD
         return -1;
     if (virConfGetValueBool(conf, "vnc_allow_host_audio", &cfg->vncAllowHostAudio) < 0)
         return -1;
+    if (virConfGetValueBool(conf, "vnc_acl", &cfg->vncACL) < 0)
+        return -1;
 
     return 0;
 }
diff -urp libvirt-5.1.0.orig/src/qemu/qemu_conf.h libvirt-5.1.0/src/qemu/qemu_conf.h
--- libvirt-5.1.0.orig/src/qemu/qemu_conf.h	2019-03-23 11:41:18.270000000 +0100
+++ libvirt-5.1.0/src/qemu/qemu_conf.h	2019-03-23 11:41:44.603000000 +0100
@@ -124,6 +124,7 @@ struct _virQEMUDriverConfig {
     bool vncTLSx509verify;
     bool vncTLSx509verifyPresent;
     bool vncSASL;
+    bool vncACL;
     char *vncTLSx509certdir;
     char *vncTLSx509secretUUID;
     char *vncListen;