CVE-2025-63679 is a buffer overflow vulnerability identified in free5gc, an open-source 5G core network implementation, specifically affecting version 4.1.0 and earlier. The vulnerability arises when the AMF component receives a specially crafted UplinkRANConfigurationTransfer message via the NG Application Protocol (NGAP) from a gNB (next-generation NodeB). Due to improper bounds checking or insufficient validation of the message payload, the AMF process crashes, leading to a denial of service. Given the critical CVSS score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), the vulnerability can be exploited remotely over the network without any authentication or user interaction, resulting in complete compromise of confidentiality, integrity, and availability of the AMF service. The AMF is a pivotal element in the 5G core, responsible for mobility management and session handling, so its disruption can severely impact network operations. Although no public exploits are currently known, the nature of the vulnerability (CWE-120: classic buffer overflow) suggests potential for remote code execution if exploited skillfully. The lack of available patches at the time of disclosure increases urgency for operators to implement interim mitigations. This vulnerability highlights risks inherent in open-source 5G core deployments, which are increasingly adopted for flexibility and cost reasons but require rigorous security validation. Organizations must scrutinize NGAP message handling and consider network segmentation and anomaly detection to mitigate exploitation risks until patches are released.

For European organizations, especially telecom operators and infrastructure providers deploying free5gc or similar open-source 5G core solutions, this vulnerability poses a significant threat. Exploitation can cause AMF process crashes, leading to denial of service and disruption of 5G network services, impacting millions of users and critical communications. The potential for remote code execution could allow attackers to gain control over core network functions, compromising subscriber data confidentiality and network integrity. This could affect emergency services, enterprise connectivity, and consumer mobile services, resulting in financial losses, reputational damage, and regulatory penalties under GDPR and telecom regulations. The disruption of 5G services could also impact industries relying on 5G connectivity such as manufacturing, transportation, and healthcare. Given the critical role of 5G in European digital infrastructure and the strategic push for 5G adoption, this vulnerability represents a high operational and security risk.

1. Immediate monitoring of NGAP traffic to detect anomalous or malformed UplinkRANConfigurationTransfer messages using deep packet inspection or protocol-aware IDS/IPS systems. 2. Implement network segmentation to isolate the AMF and other core network functions from untrusted networks and limit exposure to potentially malicious gNBs. 3. Apply strict input validation and rate limiting on NGAP messages at the network edge or within the AMF if possible. 4. Engage with free5gc maintainers and security communities to obtain patches or security updates as soon as they become available. 5. Conduct thorough code audits and fuzz testing on NGAP message handling components to identify and remediate similar vulnerabilities proactively. 6. Develop incident response plans specifically for 5G core network disruptions, including fallback procedures and rapid recovery mechanisms. 7. Consider deploying additional security controls such as runtime application self-protection (RASP) or memory protection techniques to mitigate buffer overflow exploitation. 8. Collaborate with telecom vendors and regulators to share threat intelligence and coordinate defensive measures.