Sync Under Siege: Spoofing Attack and Detection in 5G NR-V2X Synchronization

In Fifth Generation New Radio-based Vehicle-to-Everything (5G NR-V2X) systems, Vehicle-to-Vehicle (V2V) communication plays a vital role in improving road safety by allowing a timely exchange of situational awareness among vehicles. Accurate time synchronization is critical to ensure reliable message delivery, especially in out-of-coverage scenarios where cellular infrastructure and Global Navigation Satellite System (GNSS) services are not reliable. Although the 3rd Generation Partnership Project (3GPP) standard specifies synchronization mechanisms based on Sidelink Synchronization Block (SSB) and selection/reselection of a synchronization reference vehicle (SyncRef), these methods suffer from inherent vulnerabilities due to their dependence on broadcast transmissions and naive selection/reselection procedures. In this paper, a targeted spoofing attack that exploits this frailty is proposed under which malicious de-synchronization is introduced into the network. We conduct extensive simulations to evaluate the impact of our proposed attack. Our findings reveal a significant degradation in communication performance under the proposed attack, including increased collision probability, reduced throughput, and reduced Packet Reception Ratio (PRR). To counter this threat, we also propose a detection framework based on Channel Busy Ratio (CBR) and Channel occupancy Ratio (CR), which effectively distinguishes normal channel behaviors and synchronization-based attacks. The proposed detection method effectively enhances the robustness and security of NR-V2X systems against synchronization-related vulnerabilities. To the best of our knowledge, this is the first work that contributes to addressing the security issues of the synchronization procedure in NR-V2X sidelink communication.