While a significant efforts have been made in the specification and deployment of the 5th generation mobile systems (5G), there is a noticeable lack of practical experiments regarding its security. The 3GPP standardisation body has already defined numerous protocols, procedures and implementation guidelines for 5G. However, many of these requirements and procedures are missing assessment and experiments to validate their security conformance. In this paper we experiment and implement various DoS attacks in the 5G protocol stack by using a COTS 5G solution. we mainly show through these experiments that numerous potential misconfiguration and misuses pose significant threats to the security of 5G networks.