Check length of memcmp

@@ -11611,10 +11611,10 @@ send_ssi_file(struct mg_connection *conn,
     /* Handle SSI tag */
     buf[len] = 0;

-     if (!memcmp(buf + 5, "include", 7)) {
+     if ((len > 12) && !memcmp(buf + 5, "include", 7)) {
      do_ssi_include(conn, path, buf + 12, include_level + 1);
 #if !defined(NO_POPEN)
-     } else if (!memcmp(buf + 5, "exec", 4)) {
+     } else if ((len > 9) && !memcmp(buf + 5, "exec", 4)) {
      do_ssi_exec(conn, buf + 9);
 #endif /* !NO_POPEN */
     } else {