CVE-2022-38871 is a high-severity vulnerability identified in Free5gc version 3.0.5, an open-source 5G core network implementation. The vulnerability arises from the Access and Mobility Management Function (AMF) component, which is responsible for handling NAS (Non-Access Stratum) signaling messages between the user equipment (UE) and the 5G core network. Specifically, the AMF breaks or crashes when it processes malformed NAS messages. This indicates a denial-of-service (DoS) condition triggered by sending crafted NAS messages that the AMF cannot properly handle. The vulnerability is classified under CWE-400, which relates to uncontrolled resource consumption, suggesting that the malformed messages cause excessive resource usage or unhandled exceptions leading to service disruption. The CVSS v3.1 base score is 7.5, reflecting a high severity due to the network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), but a high impact on availability (A:H). No known exploits in the wild have been reported, and no patches or vendor advisories are currently linked. The lack of vendor or product information beyond Free5gc v3.0.5 limits detailed attribution, but the vulnerability clearly affects 5G core network deployments using this software version. Attackers can remotely cause denial of service by sending malformed NAS messages, potentially disrupting mobile network availability and service continuity.

For European organizations, especially mobile network operators (MNOs), telecom infrastructure providers, and enterprises deploying private 5G networks using Free5gc v3.0.5, this vulnerability poses a significant risk. Exploitation can lead to denial of service of the AMF, a critical 5G core function responsible for mobility management and session handling. This disruption can cause dropped connections, failed registrations, and degraded network performance, impacting end-users and business-critical applications relying on 5G connectivity. Given the increasing adoption of 5G in Europe for industrial automation, smart cities, and IoT, such a DoS could have cascading effects on operational technology and public services. Although no confidentiality or integrity impact is noted, availability loss in telecom infrastructure can have severe economic and reputational consequences. The vulnerability's network-level exploitability without authentication or user interaction increases the attack surface, making it a practical threat if Free5gc v3.0.5 is in active use. However, the open-source nature of Free5gc means that commercial operators may use customized or patched versions, potentially mitigating exposure. Still, smaller operators or research/test deployments may be more vulnerable.

1. Immediate mitigation involves upgrading Free5gc to a version where this vulnerability is patched. If no official patch exists, operators should monitor Free5gc repositories and community advisories for updates addressing CVE-2022-38871. 2. Implement network-level filtering to detect and block malformed NAS messages or anomalous traffic patterns targeting the AMF. This may involve deep packet inspection or protocol-aware firewalls tailored to 5G NAS signaling. 3. Deploy rate limiting and anomaly detection on the AMF interfaces to prevent resource exhaustion from malformed or excessive NAS messages. 4. Conduct thorough testing of 5G core components under malformed input scenarios to identify and remediate similar robustness issues proactively. 5. For private 5G deployments, restrict access to the AMF interfaces to trusted networks and authenticated entities only, reducing exposure to unauthenticated attacks. 6. Maintain comprehensive monitoring and alerting on AMF health and performance metrics to detect early signs of DoS conditions. 7. Engage with the Free5gc open-source community to contribute patches or share threat intelligence related to this vulnerability.