Security Vulnerabilities in 5G Non-Stand-Alone Networks: A Systematic Analysis and Attack Taxonomy

5G networks are essential for modern digital societies and are currently transitioning from 4G to 5G Stand-Alone (SA) architectures. However, 5G Non-Stand-Alone (NSA) networks are still widely deployed during this transition phase. This paper systematically analyzes the security vulnerabilities present in 5G NSA networks. By conducting an extensive literature review, the authors identify 4G-based attacks that remain applicable to 5G NSA and organize these attacks into a detailed taxonomy. The study reveals that many security and privacy enhancements are exclusive to 5G SA, leaving NSA deployments vulnerable. The authors implement and validate three impactful attacks on commercial smartphones, including an IMSI leak attack that exposes user identities without effective mitigation in current 5G NSA networks, highlighting significant privacy and security risks.