--- a/sys/netgraph7/ng_source.c
+++ b/sys/netgraph7/ng_source.c
@@ NGM_SOURCE_GET_COUNTER @@
 	    {
+		uint8_t index;
 		struct ng_source_embed_cnt_info *embed;
 
+		if (msg->header.arglen < sizeof(index)) {
+			error = EINVAL;
+			break;
+		}
+		index = *(uint8_t *)msg->data;
-		uint8_t index = *(uint8_t *)msg->data;