In this paper, the blind synchronization approach based on the Frobenius square norm behaviour (FSNB) proposed in [1]-[3] is extended to the case of several users in multirate CDMA transmissions. It consists in estimating the FSNB criterion maxima (synchronization peaks) positions, and it allows one to estimate desynchronization and transmissions delay times. We prove that, the extented-FSNB criterion is a powerful tool for blind synchronization. We also detail the synchronization peaks masking which degrades its performances especially at very low SNRs, and show how to proceed in this case. Simulation results illustrate sequences identification and symbols recovering, after synchronizing using the extended-FSNB.