Channel.prototype.signal = function(signalName) {
  if (this.server)
    throw new Error('Client-only method called in server mode');

  if (this.type === 'session'
      && this.writable
      && this.outgoing.state === 'open')
    return this._client._sshstream.signal(this.outgoing.id, signalName);

  return true;
};
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.