--- ./lib/rrd.php.orig	2014-08-11 17:34:23.000000000 -0700
+++ ./lib/rrd.php	2014-08-11 17:34:23.000000000 -0700
@@ -1343,20 +1343,20 @@
 		$need_rrd_nl = TRUE;
 
 		if ($graph_item_types{$graph_item["graph_type_id"]} == "COMMENT") {
+			# perform variable substitution first (in case this will yield an empty results or brings command injection problems)
+			$comment_arg = rrd_substitute_host_query_data($graph_variables["text_format"][$graph_item_id], $graph, $graph_item);
+			# next, compute the argument of the COMMENT statement and perform injection counter measures
+			if (trim($comment_arg) == '') { # an empty COMMENT must be treated with care
+				$comment_arg = cacti_escapeshellarg(' ' . $hardreturn[$graph_item_id]);
+			} else {
+				$comment_arg = cacti_escapeshellarg($comment_arg . $hardreturn[$graph_item_id]);
+			}
+
+			# create rrdtool specific command line
 			if (read_config_option("rrdtool_version") != "rrd-1.0.x") {
-				$comment_string = $graph_item_types{$graph_item["graph_type_id"]} . ":" . str_replace(":", "\:", cacti_escapeshellarg($graph_variables["text_format"][$graph_item_id] . $hardreturn[$graph_item_id])) . " ";
-				if (trim($comment_string) == 'COMMENT:"\n"') {
-					$txt_graph_items .= 'COMMENT:" \n"'; # rrdtool will skip a COMMENT that holds a NL only; so add a blank to make NL work
-				} else if (trim($comment_string) != "COMMENT:\"\"") {
-					$txt_graph_items .= rrd_substitute_host_query_data($comment_string, $graph, $graph_item);
-				}
+				$txt_graph_items .= $graph_item_types{$graph_item["graph_type_id"]} . ":" . str_replace(":", "\:", $comment_arg) . " ";
 			}else {
-				$comment_string = $graph_item_types{$graph_item["graph_type_id"]} . ":" . cacti_escapeshellarg($graph_variables["text_format"][$graph_item_id] . $hardreturn[$graph_item_id]) . " ";
-				if (trim($comment_string) == 'COMMENT:"\n"') {
-					$txt_graph_items .= 'COMMENT:" \n"'; # rrdtool will skip a COMMENT that holds a NL only; so add a blank to make NL work
-				} else if (trim($comment_string) != "COMMENT:\"\"") {
-					$txt_graph_items .= rrd_substitute_host_query_data($comment_string, $graph, $graph_item);
-				}
+				$txt_graph_items .= $graph_item_types{$graph_item["graph_type_id"]} . ":" . $comment_arg . " ";
 			}
 		}elseif (($graph_item_types{$graph_item["graph_type_id"]} == "GPRINT") && (!isset($graph_data_array["graph_nolegend"]))) {
 			$graph_variables["text_format"][$graph_item_id] = str_replace(":", "\:", $graph_variables["text_format"][$graph_item_id]); /* escape colons */