CVE-2026-1684 identifies a denial of service (DoS) vulnerability in the Free5GC Session Management Function (SMF) component, specifically affecting versions 4.0 and 4.1.0. The vulnerability resides in the HandleReports function of the PFCP UDP Endpoint, located in the /internal/context/pfcp_reports.go source file. PFCP (Packet Forwarding Control Protocol) is critical for control plane communication between the SMF and User Plane Function (UPF) in 5G core networks. The issue arises from improper handling or validation of PFCP reports, which an attacker can manipulate remotely without authentication or user interaction. This manipulation can cause the SMF process to crash or become unresponsive, resulting in denial of service. The CVSS 4.0 base score is 6.9 (medium severity), reflecting the network attack vector, low attack complexity, no privileges or user interaction required, and limited impact on availability. No known exploits have been reported yet, but the vulnerability poses a risk to the availability of 5G core network services that depend on Free5GC SMF. Since Free5GC is an open-source 5G core implementation, it is used in research, testing, and some production environments, making this vulnerability relevant for operators and vendors deploying Free5GC-based infrastructures.

For European organizations, especially telecom operators and network service providers deploying Free5GC SMF in their 5G core networks, this vulnerability could lead to service disruptions. A successful DoS attack could cause session management failures, impacting subscriber connectivity, session establishment, and mobility management. This may result in degraded user experience, loss of revenue, and potential regulatory non-compliance due to service outages. Critical infrastructure relying on 5G connectivity, such as smart grids, transportation, and emergency services, could also be indirectly affected. The remote and unauthenticated nature of the attack increases the risk, as threat actors could exploit this vulnerability from outside the network perimeter. Although no exploits are currently known, the medium severity score and the essential role of SMF in 5G core networks necessitate proactive mitigation to prevent potential disruptions.

European organizations should immediately assess their Free5GC SMF deployments and upgrade to a patched version once available from the Free5GC project. In the absence of an official patch, organizations can implement network-level protections such as filtering and rate-limiting PFCP traffic to mitigate potential exploitation attempts. Deploying anomaly detection systems to monitor unusual PFCP message patterns can help identify exploitation attempts early. Isolating the SMF component within segmented network zones and restricting PFCP UDP port access to trusted network elements reduces exposure. Regularly auditing and updating 5G core network components, including open-source projects like Free5GC, is critical. Additionally, organizations should engage with Free5GC community channels to track patch releases and vulnerability disclosures. Incident response plans should be updated to include scenarios involving SMF DoS attacks to ensure rapid recovery.