diff --git a/src/wps/wps_upnp.c b/src/wps/wps_upnp.c
index 7d4b74399..ab685d52e 100644
--- a/src/wps/wps_upnp.c
+++ b/src/wps/wps_upnp.c
@@ -328,9 +328,14 @@ static void subscr_addr_add_url(struct subscription *s, const char *url,
 	int rerr;
 	size_t host_len, path_len;
 
-	/* url MUST begin with http: */
-	if (url_len < 7 || os_strncasecmp(url, "http://", 7))
+	/* URL MUST begin with HTTP scheme. In addition, limit the length of
+	 * the URL to 700 characters which is around the limit that was
+	 * implicitly enforced for more than 10 years due to a bug in
+	 * generating the event messages. */
+	if (url_len < 7 || os_strncasecmp(url, "http://", 7) || url_len > 700) {
+		wpa_printf(MSG_DEBUG, "WPS UPnP: Reject an unacceptable URL");
 		goto fail;
+	}
 	url += 7;
 	url_len -= 7;
 
diff --git a/src/wps/wps_upnp_event.c b/src/wps/wps_upnp_event.c
index d7e6edcc6..08a23612f 100644
--- a/src/wps/wps_upnp_event.c
+++ b/src/wps/wps_upnp_event.c
@@ -147,7 +147,8 @@ static struct wpabuf * event_build_message(struct wps_event_ *e)
 	struct wpabuf *buf;
 	char *b;
 
-	buf = wpabuf_alloc(1000 + wpabuf_len(e->data));
+	buf = wpabuf_alloc(1000 + os_strlen(e->addr->path) +
+			   wpabuf_len(e->data));
 	if (buf == NULL)
 		return NULL;
 	wpabuf_printf(buf, "NOTIFY %s HTTP/1.1\r\n", e->addr->path);