Lenovo have found a backdoor in the firmware of RackSwitch and BladeCenter networking switches. The backdoor was apparently added back in 2004 by Nortel. The switch firmware at the time was maintained by Nortel hence Lenovo place the blame there. The name of the backdoor is “HP backdoor”
Lenovo have released a update to the firmware to remove the backdoor. Lenovo have also said that the backdoor is hard to exploit. This issues is documented as CVE-2017-3765.