    const sendKA = () => {
      if (++kacount > kacountmax) {
        clearInterval(katimer);
        if (sock.readable) {
          const err = new Error('Keepalive timeout');
          err.level = 'client-timeout';
          this.emit('error', err);
          sock.destroy();
        }
        return;
      }
      if (sock.writable) {
        // Append dummy callback to keep correct callback order
        callbacks.push(resetKA);
        proto.ping();
      } else {
        clearInterval(katimer);
      }
    };
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.