The vulnerability identified as CVE-2025-69247 affects the go-upf component of free5GC, an open-source 5G core network implementation. The go-upf module serves as the User Plane Function (UPF), responsible for forwarding user data in 5G networks. The flaw is a heap-based buffer overflow (CWE-122) triggered by processing a PFCP (Packet Forwarding Control Protocol) Session Modification Request containing an invalid SDF (Service Data Flow) Filter length field. When the UPF parses this malformed request, it writes beyond the allocated heap buffer boundaries, corrupting memory. This corruption leads to a crash of the UPF process, causing denial of service (DoS) for all user equipment (UE) connected through the affected UPF. Additionally, the failure of the UPF can cascade to the Session Management Function (SMF), which relies on the UPF for session control, potentially amplifying network disruption. The vulnerability requires no authentication or user interaction and can be exploited remotely by an attacker with network access to the UPF. The CVSS 4.0 base score is 2.7, reflecting the limited scope of impact (availability only) and the absence of confidentiality or integrity compromise. No known exploits are currently reported in the wild. The issue is resolved in free5GC go-upf version 1.2.8, which includes proper validation of the SDF Filter length to prevent buffer overflow.

The primary impact of this vulnerability is a denial of service condition affecting the User Plane Function in 5G networks using free5GC. A successful exploit results in the UPF crashing, which disrupts data forwarding for all connected user devices, effectively cutting off their network access. This can degrade service quality and availability for end users and may lead to significant operational disruptions for mobile network operators relying on free5GC. The cascading effect on the SMF can further destabilize session management and control plane functions, potentially causing broader network outages. Although the vulnerability does not expose data or allow unauthorized access, the loss of availability in critical 5G infrastructure components can have severe consequences, especially for enterprises and services dependent on continuous 5G connectivity. The low CVSS score suggests limited risk in terms of confidentiality and integrity, but the operational impact on network availability is non-trivial. Organizations deploying free5GC UPF in production environments are at risk of service interruptions if unpatched.

To mitigate this vulnerability, organizations should immediately upgrade the free5GC go-upf component to version 1.2.8 or later, where the heap buffer overflow has been fixed. Network operators should implement strict input validation and filtering at the network perimeter to block malformed PFCP messages from untrusted sources. Deploying network segmentation and access controls can limit exposure of the UPF to potentially malicious actors. Monitoring and alerting on abnormal PFCP traffic patterns can help detect attempted exploitation. Additionally, implementing redundancy and failover mechanisms for UPF instances can reduce the impact of a single node failure. Regularly auditing and updating all 5G core network components, including open-source projects like free5GC, is critical to maintaining security posture. Finally, operators should coordinate with vendors and community projects to stay informed about patches and vulnerability disclosures.