After the discovery of neutrino oscillations, the smallness of the Standard Model neutrino masses is one of the most intriguing questions in neutrino physics today. A leading theoretical candidate to explain this phenomenon is known as the "seesaw" mechanism, in which a new heavy Majorana neutrino (N) state is postulated. Here we present the recent efforts to search for this postulated heavy neutrino at the CMS collaboration using the LHC Run 2 data. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to a total integrated luminosity of 137 fb-1. The variety of search strategies, covering various N production modes I.e., via charged current Drell-Yan, Wγ fusion and same-sign WW fusion processes, producing final states with two or three leptons and with different types of reconstructed jets, leads to a wide range of search sensitivity of N mass ranging from 1 GeV up to 25 TeV. We also discuss the future prospect of follow-up searches which are now vividly ongoing and expected to be published.