In this paper, we investigate the secondary network physical layer security under the outage constraint of the primary user (PU) receiver and interference from the PU transmitter to the secondary network. In particular, a secondary user (SU) transmitter sends confidential messages to trusted multiple SU receivers (SU-Rxs) in the presence of multiple eavesdroppers (EAVs). Further, we exploit multiuser diversity where the SU-Rx with best channel condition is scheduled for transmission. Then, analytical expressions of the probability of existence of non-zero secrecy capacity and secrecy outage probability are obtained. Analytical and simulation results are provided to evaluate the effect of the number of SU-Rxs and number of EAVs on the secondary system. Interestingly, the numerical results show that the interference from the primary network to the secondary network is an important parameter to improve the secondary network security.