Status report of the upgrade of the CMS muon system with Triple-GEM detectors

For the High Luminosity LHC CMS is planning to install new large size Triple-GEM detectors, equipped with a new readout system in the forward region of its muon system (1.5 < vertical bar eta vertical bar < 2.2). In this note we report on the status of the project, the main achievements regarding the detectors as well as the electronics and readout system.