The vulnerability stems from improper input validation in the HandleUpdate function located in "/sbi/parameter_provision.go" of free5gc v4.0.1. When a crafted request reaches this endpoint, the service fails to correctly verify the input, resulting in a crash that renders the affected component or the entire network element unavailable. This denial of service can interrupt critical mobile network functions that rely on free5gc, potentially taking a deployed network offline until the defect is remedied or the server is restarted.

free5gc versions that include the vulnerable HandleUpdate implementation, specifically the 4.0.1 release. Any deployment of this version within an operational 5G core network is susceptible unless a patch or newer version is applied.

The CVSS score is 7.5, and the EPSS score is < 1%, indicating a low exploitation likelihood. The vulnerability has not been reported as a known exploited instance in CISA’s KEV catalog. Based on the description, the attack requires the ability to send a specially crafted input to the HandleUpdate API, which is typically exposed over a network interface accessible to the Internet or an internal network. An attacker with network access to that interface could trigger the crash repeatedly, leading to repeated service outages. The fixed weakness is improper input validation, a high‑level flaw that can be leveraged without privileged access.