      function onExit(code, signal) {
        sftp.removeListener('ready', onReady);
        sftp.removeListener('error', onError);
        var msg;
        if (typeof code === 'number') {
          msg = 'Received exit code '
                + code
                + ' while establishing SFTP session';
        } else {
          msg = 'Received signal '
                + signal
                + ' while establishing SFTP session';
        }
        var err = new Error(msg);
        err.code = code;
        err.signal = signal;
        cb(err);
      }
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.