diff --git a/src/server/dial_server.c b/src/server/dial_server.c
index 43413b4..ca3ee5e 100644
--- a/src/server/dial_server.c
+++ b/src/server/dial_server.c
@@ -118,7 +118,7 @@
                              const char *app_name,
                              const char *origin_header) {
     char additional_data_param[256] = {0, };
-    char body[DIAL_MAX_PAYLOAD + sizeof(additional_data_param) + 2] = {0, };
+    char body[DIAL_MAX_PAYLOAD] = {0, };
     DIALApp *app;
     DIALServer *ds = request_info->user_data;
     int body_size;
@@ -143,15 +143,17 @@
             in_port_t dial_port = DIAL_get_port(ds);
 
             if (app->useAdditionalData) {
-                if (body_size != 0) {
-                    strcat(body, "&");
-                }
                 // Construct additionalDataUrl=http://host:port/apps/app_name/dial_data
-                sprintf(additional_data_param,
-                        "additionalDataUrl=http%%3A%%2F%%2Flocalhost%%3A%d%%2Fapps%%2F%s%%2Fdial_data%%3F",
+                snprintf(additional_data_param, sizeof(additional_data_param),
+                        "%sadditionalDataUrl=http%%3A%%2F%%2Flocalhost%%3A%d%%2Fapps%%2F%s%%2Fdial_data%%3F",
+                        (body_size != 0) ? "&" : "",
                         dial_port, app_name);
-                strcat(body, additional_data_param);
-                body_size = strlen(body);
+                if ((body_size + strlen(additional_data_param)) < DIAL_MAX_PAYLOAD) {
+                    strcat(body, additional_data_param);
+                    body_size = strlen(body);
+                } else {
+                    fprintf(stderr, "payload too small for additional data\n");
+                }
             }
             fprintf(stderr, "Starting the app with params %s\n", body);
             app->state = app->callbacks.start_cb(ds, app_name, body, body_size,
@@ -168,7 +170,11 @@
                         laddr, dial_port, app_name, origin_header);
                 // copy the payload into the application struct
                 memset(app->payload, 0, DIAL_MAX_PAYLOAD);
-                memcpy(app->payload, body, body_size);
+                if (body_size<=DIAL_MAX_PAYLOAD) {
+                    memcpy(app->payload, body, body_size);
+                } else {
+                    fprintf(stderr, "payload too small for body of %d bytes\n", body_size);
+                }
             } else {
                 mg_send_http_error(conn, 503, "Service Unavailable",
                                    "Service Unavailable");