  The fifth generation of mobile broadband is more than just an evolution to
provide more mobile bandwidth, massive machine-type communications, and
ultra-reliable and low-latency communications. It relies on a complex, dynamic
and heterogeneous environment that implies addressing numerous testing and
security challenges. In this paper we present 5Greplay, an open-source 5G
network traffic fuzzer that enables the evaluation of 5G components by
replaying and modifying 5G network traffic by creating and injecting network
scenarios into a target that can be a 5G core service (e.g., AMF, SMF) or a RAN
network (e.g., gNodeB). The tool provides the ability to alter network packets
online or offline in both control and data planes in a very flexible manner.
The experimental evaluation conducted against open-source based 5G platforms,
showed that the target services accept traffic being altered by the tool, and
that it can reach up to 9.56 Gbps using only 1 processor core to replay 5G
traffic.
