CVE-2026-30653 is a vulnerability identified in Free5GC, an open-source 5G core network implementation, specifically affecting version 4.2.0 and earlier. The flaw resides in the HandleAuthenticationFailure function of the Access and Mobility Management Function (AMF) component. This function is responsible for processing authentication failure events during the 5G authentication procedure. The vulnerability allows a remote attacker to trigger a denial of service (DoS) condition by sending crafted messages that cause the AMF to exhaust resources or crash, leading to service unavailability. Classified under CWE-400 (Uncontrolled Resource Consumption), the issue stems from improper handling of authentication failure events, which can be exploited without any authentication or user interaction, making it remotely exploitable over the network. The CVSS v3.1 base score of 7.5 indicates a high severity primarily due to the impact on availability (A:H), with no impact on confidentiality or integrity, and no privileges or user interaction required. No patches or known exploits are currently reported, but the vulnerability poses a significant risk to 5G core network operators using Free5GC, potentially disrupting mobile network services and affecting subscriber connectivity and mobility management.

The primary impact of CVE-2026-30653 is a denial of service condition in the 5G core network's AMF component, which can disrupt authentication procedures and mobility management for subscribers. This can lead to partial or complete unavailability of 5G network services, affecting voice, data, and signaling traffic. For telecommunications providers and enterprises relying on Free5GC, this can result in degraded customer experience, loss of revenue, and reputational damage. The disruption of authentication processes may also impact lawful interception and lawful access capabilities. Given the critical role of the AMF in 5G core architecture, prolonged or repeated exploitation could cause widespread network instability. Although no confidentiality or integrity compromise is indicated, the availability impact alone is significant, especially for critical infrastructure and emergency services relying on 5G connectivity. The vulnerability could also be leveraged as part of a larger attack chain to amplify disruption or distract from other malicious activities.

Organizations using Free5GC should immediately assess their exposure to this vulnerability. Specific mitigation steps include: 1) Monitor AMF logs and network traffic for unusual authentication failure patterns or spikes that may indicate exploitation attempts. 2) Restrict network access to the AMF component by implementing strict firewall rules and network segmentation to limit exposure to untrusted or external sources. 3) Deploy rate limiting and anomaly detection mechanisms on signaling interfaces to prevent resource exhaustion from malformed or excessive authentication failure messages. 4) Engage with Free5GC maintainers or community to obtain patches or updates addressing this vulnerability as soon as they become available. 5) Conduct thorough testing of updated Free5GC versions in controlled environments before production deployment. 6) Implement redundancy and failover mechanisms in the 5G core network to maintain service continuity in case of AMF failure. 7) Educate network operations teams about this vulnerability and establish incident response procedures to quickly react to potential exploitation attempts. These targeted actions go beyond generic advice by focusing on the specific component and attack vector involved.