CVE-2025-69232 identifies an improper input validation vulnerability (CWE-20) in the go-upf component of free5GC, an open-source 5G core network implementation. The vulnerability exists in versions up to and including 1.2.6 of go-upf and SMF versions up to 1.4.0. The issue arises when the User Plane Function (UPF) improperly processes malformed PFCP (Packet Forwarding Control Protocol) Association Setup Requests from remote attackers. Instead of rejecting malformed requests, the UPF accepts them, which causes it to enter an inconsistent internal state. This inconsistent state triggers subsequent legitimate requests to cause the Session Management Function (SMF) to repeatedly attempt reconnections, creating loops that degrade service availability. The vulnerability requires no privileges, authentication, or user interaction, making it remotely exploitable over the network. While the CVSS 4.0 base score is 2.7 (low severity), reflecting limited direct impact on confidentiality, integrity, or availability, the practical effect on 5G core network stability and service continuity can be substantial. No known exploits are currently in the wild, and a patch is in development but not yet released. No application-level workarounds exist, so affected deployments must monitor for official updates and plan timely patching to restore protocol compliance and input validation robustness.

The primary impact of this vulnerability is denial of service (DoS) within the 5G core network infrastructure, specifically affecting the UPF and SMF components of free5GC deployments. Disruption of these core network functions can degrade or interrupt mobile network services, affecting voice, data, and signaling traffic for subscribers. This can lead to service outages, reduced network reliability, and potential loss of revenue and customer trust for mobile network operators using free5GC. Because 5G networks are critical infrastructure supporting not only consumer communications but also industrial, emergency, and governmental applications, the impact extends beyond typical telecom service degradation. The vulnerability's ease of exploitation without authentication increases risk, especially in environments where network access is not tightly controlled. However, the low CVSS score indicates limited impact on confidentiality or integrity, and the vulnerability does not allow remote code execution or data compromise. The absence of known exploits in the wild reduces immediate risk but does not eliminate the potential for future attacks once the vulnerability becomes widely known.

Organizations using free5GC with affected go-upf (<=1.2.6) and SMF (<=1.4.0) components should prepare to apply the official patch as soon as it is released by the free5GC project. Until then, network administrators should implement strict network segmentation and access controls to limit exposure of the UPF and SMF interfaces to untrusted networks. Monitoring and anomaly detection should be enhanced to identify unusual PFCP traffic patterns or repeated reconnection attempts indicative of exploitation attempts. Deploying upstream filtering or protocol validation proxies that can detect and block malformed PFCP Association Setup Requests may provide temporary mitigation. Additionally, operators should review and harden their 5G core network configurations to minimize attack surface and ensure logging is enabled for forensic analysis. Coordination with vendors and participation in relevant security communities will help ensure timely awareness of patch availability and exploitation trends.