The vulnerability identified as CVE-2025-69248 affects the Access and Mobility Management Function (AMF) component of free5GC, an open-source 5G core network implementation. The root cause is improper validation of array indices (CWE-129) when handling NAS Registration Requests, specifically those containing malformed 5GS Mobile Identities. This improper validation leads to a buffer overflow condition, which can be triggered remotely by unauthenticated attackers sending specially crafted NAS messages. Exploitation results in a crash of the AMF service, causing a denial of service (DoS) that disrupts the 5G core network's ability to manage user mobility and access. The vulnerability affects all free5GC AMF versions up to and including 1.4.1. The CVSS 4.0 base score is 6.6, reflecting medium severity due to network attack vector, no required privileges or user interaction, but with a high impact on availability. The vulnerability does not affect confidentiality or integrity directly. The free5GC project has addressed this issue in a patch available in pull request 43 of the free5gc/nas repository. No direct workarounds exist at the application level, making patching the primary mitigation. No known exploits have been reported in the wild, but the potential impact on 5G core network availability is significant.

The primary impact of this vulnerability is a denial of service condition in the 5G core network's AMF service, which is critical for managing user registration, mobility, and access control. A successful attack can cause the AMF to crash, disrupting network operations and potentially leading to service outages for subscribers relying on the affected 5G network. This can affect telecommunications providers deploying free5GC, especially those using it in production or test environments. The disruption could impact end-users' ability to connect or maintain sessions on the 5G network, affecting business continuity and user experience. Given the AMF's central role in 5G core architecture, prolonged outages could have cascading effects on other network functions and services. Although no known exploits are currently active, the vulnerability's remote and unauthenticated nature makes it a significant risk if weaponized. Organizations relying on free5GC must consider the operational and reputational risks associated with potential service disruptions.

The definitive mitigation is to apply the official patch provided by the free5GC project, specifically the fix included in pull request 43 of the free5gc/nas repository. Organizations should update their AMF component to a version later than 1.4.1 where this vulnerability is resolved. In addition, network operators should implement network-level protections such as filtering and anomaly detection to identify and block malformed NAS Registration Requests that could exploit this vulnerability. Deploying intrusion detection/prevention systems (IDS/IPS) with signatures targeting malformed NAS messages can help mitigate exploitation attempts. Monitoring AMF service logs and network traffic for unusual registration request patterns can provide early warning signs of exploitation attempts. Since no application-level workarounds exist, patching remains the critical step. Operators should also ensure robust incident response plans are in place to quickly recover AMF services in case of a DoS event. Regular security audits and vulnerability scanning of 5G core components can help identify and remediate similar issues proactively.