CVE-2026-1976 identifies a null pointer dereference vulnerability in the Free5GC open-source 5G core network implementation, specifically within the SessionManagementFunction (SMF) component's SessionDeletionResponse function. This flaw arises when the function improperly handles certain inputs or states, leading to dereferencing a null pointer. Exploiting this vulnerability remotely requires no authentication or user interaction, making it accessible to unauthenticated attackers over the network. The consequence is a denial-of-service (DoS) condition, where the affected SMF process may crash or become unresponsive, disrupting session management in the 5G core network. Free5GC versions 4.0 and 4.1.0 are confirmed vulnerable. Although no active exploitation has been observed in the wild, a public exploit is available, increasing the risk of future attacks. The vulnerability has a CVSS 4.0 base score of 6.9 (medium severity), reflecting its network attack vector, lack of required privileges, and impact primarily on availability. The SMF is critical for managing user sessions and mobility in 5G networks; thus, its disruption can degrade or halt 5G service delivery. No patches were linked in the provided data, but the vendor has suggested installing updates to remediate the issue. Given the open-source nature of Free5GC, organizations using it should monitor for official patches and advisories.

The primary impact of CVE-2026-1976 is on the availability of 5G core network services managed by Free5GC's SMF component. For European telecommunications providers and enterprises deploying Free5GC, exploitation could lead to denial of service, causing session management failures and potential service outages. This disruption can affect end-users relying on 5G connectivity for critical communications, IoT applications, and enterprise services. The vulnerability does not directly compromise confidentiality or integrity but can degrade network reliability and trust. Given the increasing adoption of 5G infrastructure across Europe, especially in countries investing heavily in digital transformation and smart city initiatives, the impact could extend to economic and operational domains. Additionally, the remote and unauthenticated nature of the exploit increases the risk of opportunistic attacks from malicious actors. Although no active exploitation is reported, the availability of a public exploit elevates the threat level, necessitating proactive mitigation to avoid service degradation or reputational damage.

1. Apply official patches or updates from the Free5GC project as soon as they become available to address the null pointer dereference in the SMF component. 2. Implement network-level protections such as firewall rules and intrusion detection systems to monitor and restrict anomalous traffic targeting the SMF interfaces. 3. Employ redundancy and failover mechanisms for the SMF and other 5G core components to maintain service continuity in case of crashes. 4. Conduct regular security audits and code reviews of Free5GC deployments to identify and remediate potential vulnerabilities early. 5. Monitor logs and system behavior for signs of crashes or abnormal session deletion responses that could indicate exploitation attempts. 6. Limit exposure of the SMF network interfaces to untrusted networks, using segmentation and VPNs where appropriate. 7. Engage with the Free5GC community and security advisories to stay informed about emerging threats and patches. These steps go beyond generic advice by focusing on the specific component and operational context of Free5GC in 5G networks.