84 4G and 5G Core Flaws: API Session Risk Analysis

Your phone's signal bars are the decoy, the cheerful little staircase icon telling you everything is fine while the real machinery argues in a back room. The more interesting risk lives deeper in the carrier core, where signaling interfaces and session state decide whether connectivity behaves like infrastructure or like a haunted filing cabinet. According to The Hacker News, researchers reported 84 flaws in 4G and 5G cores, including a session hijacking flaw. That is not a radio story. That is a core network story, which is worse in the quiet, paperwork covered way security engineers have learned to fear. The useful lesson is not that 5G is doomed, please return to smoke signals. It is that telecom security cannot stop at the air interface. Session management, core network APIs, and implementation hardening are now part of the systemic risk map, especially as carrier cores become more software defined and cloud native. Somewhere, a vendor is preparing a sentence about taking security seriously. My scoreboard has fresh batteries.

What happened inside the core,

according to The Hacker News The Hacker News, citing an academic study from researchers at Singapore's Nanyang Technological University, reported a disclosed "widespread class" of vulnerabilities affecting 4G and 5G core networks. The report says successful exploitation could trigger denial of service and, in some cases, session hijacking that lets an attacker seize control of a user's network session. The study examined signaling interfaces in LTE and 5G core networks, including two LTE implementations, Open5GS and OpenAirInterface, and five 5G implementations, Open5GS, free5GC, OpenAirInterface, SD-Core, and eUPF. The protocols named in the report are GTP-C and Packet Forwarding Control Protocol, the kind of plumbing that rarely gets a keynote but absolutely gets to ruin everyone's week.

The root cause is trust,

according to the arXiv paper The arXiv paper behind the findings names the pattern implicit trust errors, or iTrue vulnerabilities. Its abstract says cellular core networks historically relied on physical isolation, with interfaces between core components operating inside an assumed trust zone. As core networks transition to cloud native deployments, the paper says that assumption weakens, expanding the attack surface and letting external adversaries reach interfaces that were previously treated as internal. Translation: the walls moved, but the software still thinks it lives in a locked building. The arXiv authors describe recurring blind trust among core network components. Components may skip syntactic validation, fail to enforce semantic invariants, or allocate resources without checking availability. That trio is not glamorous, but it is how infrastructure failures grow teeth. A malformed message is bad. A malformed message accepted by a trusted component that then changes session behavior is the thriller plot version of bad.

APIs and privilege are the quiet risk multipliers,

according to 5GAC Analyzer A separate paper, Identifying Over-Privilege Between 5G Core Network Functions, helps explain why this class of problem is bigger than one bug list. The authors write that 5G moves the cellular core from specialized hardware into software based cloud native network functions, while 3GPP defines an access control policy meant to protect network functions from one another and from third party network applications. Their manual review context matters because policy, privilege, and implementation now meet in the same room. If one of them lies, the others may politely believe it. The 5GAC Analyzer paper says a manual 3GPP review identified an over privilege flaw that exposed cryptographic keys to all network functions. The authors then used static program analysis to extract network function behavior from four 5G core implementations and compare it with what the 3GPP policy permits. They found two previously unknown over privilege instances that could lead to denial of service and sensitive data extraction, and reported the findings to the GSMA, which confirmed their significance. That is the larger pattern: core network APIs and policies need least privilege discipline, not vibes and a diagram with a padlock on it.

What it actually means for you,

according to the research For ordinary users, this is not a patch your phone can install over coffee. The affected surface described by The Hacker News and the arXiv paper sits in carrier core implementations and signaling interfaces, where users have very little direct control. The practical takeaway is to be cautious about claims that mobile network security is only about the radio link, because the session layer and core implementation details matter to privacy and availability too. If your organization buys private 5G, telecom services, or managed connectivity, ask vendors how they validate core signaling inputs, enforce semantic invariants, check resource availability, and segment internal interfaces. For operators and vendors, the work points toward a better testing agenda. Treat internal components as mutually suspicious, especially in cloud native deployments. Pair protocol fuzzing and semantic validation with access control review, because a network function with too much privilege is not a feature, it is a future incident report with nicer formatting. Watch for follow on CVEs, implementation fixes, and whether carrier core security programs start treating APIs, sessions, and privilege boundaries as first class risk surfaces. The internet may not completely fall apart today, which is what passes for optimism on this beat.