CVE-2026-1683 is a vulnerability identified in the Free5GC Session Management Function (SMF) component, specifically in the HandlePfcpSessionReportRequest function located in the internal/pfcp/handler/handler.go file. Free5GC is an open-source 5G core network implementation widely used for research, development, and some production environments. The SMF is responsible for managing session contexts and controlling user plane resources in 5G networks. The vulnerability arises from improper handling of PFCP (Packet Forwarding Control Protocol) session report requests, which can be manipulated by an attacker to trigger a denial of service (DoS) condition. This manipulation causes the SMF process to crash or become unresponsive, disrupting session management and potentially impacting the availability of 5G services. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing the risk profile. The CVSS v4.0 score of 6.9 (medium severity) reflects the ease of remote exploitation (attack vector network, low attack complexity) and the impact limited to availability loss without affecting confidentiality or integrity. Although no exploits have been observed in the wild yet, the public disclosure of the vulnerability increases the likelihood of future exploitation attempts. The recommended remediation is to apply patches provided by the Free5GC project once available. In the interim, network operators should consider filtering or rate-limiting PFCP session report requests to mitigate attack vectors. The vulnerability highlights the importance of robust input validation and error handling in critical 5G core network components to maintain service continuity.

For European organizations, particularly telecom operators and 5G service providers deploying Free5GC SMF, this vulnerability poses a risk of service disruption through denial of service attacks. Exploitation could lead to session management failures, resulting in dropped connections, degraded network performance, or complete unavailability of 5G services for end-users. This can affect critical communications infrastructure, emergency services, and enterprise customers relying on 5G connectivity. The impact extends to potential reputational damage and regulatory scrutiny under frameworks like the NIS Directive and GDPR if service outages affect customer data processing or availability. Given the remote exploitability without authentication, attackers can launch DoS attacks from external networks, increasing the threat surface. While the vulnerability does not compromise data confidentiality or integrity, the loss of availability in core network functions can have cascading effects on dependent services and applications. European telecom operators must prioritize patching and implement network-level protections to maintain resilience against such disruptions.

1. Apply official patches from the Free5GC project as soon as they are released to address the vulnerability in the HandlePfcpSessionReportRequest function. 2. Implement network-level filtering and rate limiting on PFCP session report requests to detect and block malformed or excessive traffic that could trigger the DoS condition. 3. Deploy anomaly detection systems within the 5G core network to monitor PFCP traffic patterns and alert on suspicious activities indicative of exploitation attempts. 4. Conduct regular security audits and code reviews of the Free5GC SMF component to identify and remediate similar input validation and error handling weaknesses. 5. Isolate critical 5G core functions in segmented network zones with strict access controls to limit exposure to external threats. 6. Collaborate with vendors and the open-source community to stay informed about updates, patches, and emerging threats related to Free5GC components. 7. Develop and test incident response plans specifically for 5G core network disruptions to minimize downtime and service impact during attacks.