The CMS tracker and vertexing before and after the upgrade

The CMS detectors core is composed of the largest silicon detector ever built. This tracker consists of a hybrid pixel detector with 66 million channels and a 200 m^2 silicon strip detector with 10 million read out channels. Thanks to its fine granularity, it can perform excellent tracks and vertices reconstruction, essential objects in physics analyses. However, the next LHC upgrades will expose CMS to a higher number of simultaneous inelastic collisions per crossing (pile-up events). In order to maintain such performances, the pixel detector will be upgraded. In this contribution, we describe the current tracker performances, driven by the resolution and efficiency of the tracks and vertices reconstruction. We will then highlight the significant role of secondary vertices in physics analyses, especially for the identification of jets coming from the hadronization of a b quark, fundamental in new particles and new physics searches. Finally, we will describe the foreseen upgrades of the tracker and emphasis the expected performance improvements in a high luminosity and high pile-up environment