      function reqCb(err) {
        if (err) {
          chan.close();
          cb(err);
          return;
        }
        if (todo.length)
          todo.shift()();
      }
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.