CVE-2025-2566 is a critical security vulnerability identified in Kaleris Navis N4 Ultra Light Client (ULC), specifically involving unsafe Java deserialization (CWE-502). The vulnerability allows an unauthenticated attacker to send specially crafted requests that exploit the deserialization process on the server side, leading to arbitrary code execution. Java deserialization vulnerabilities occur when untrusted data is deserialized without proper validation or sanitization, enabling attackers to inject malicious objects that the application processes, resulting in control over the execution flow. In this case, the Navis N4 ULC component does not enforce sufficient checks on incoming serialized data, making it susceptible to remote code execution (RCE) without requiring any authentication or user interaction. The CVSS 4.0 base score of 9.3 reflects the high severity, with attack vector being network-based, no privileges or user interaction required, and a high impact on confidentiality, integrity, and availability. The vulnerability affects version 0 of the product, which likely indicates initial or early releases. No patches or mitigations have been published yet, and there are no known exploits in the wild at the time of disclosure. Given the nature of the vulnerability, exploitation could allow attackers to fully compromise affected servers, potentially leading to data breaches, operational disruption, or lateral movement within enterprise networks.

For European organizations using Kaleris Navis N4, this vulnerability poses a significant risk. Navis N4 is a terminal operating system widely used in maritime logistics and port operations, critical sectors for European trade and supply chains. Successful exploitation could lead to unauthorized control over terminal operations, disruption of cargo handling, and compromise of sensitive operational data. This could result in severe economic impact due to delays, loss of trust, and regulatory penalties under GDPR if personal or business data is exposed. Additionally, the ability to execute arbitrary code remotely without authentication increases the risk of ransomware deployment or espionage activities targeting critical infrastructure. The impact extends beyond individual organizations to national and regional supply chain resilience, especially in countries with major port facilities relying on Navis N4 for terminal management.

Given the absence of official patches, European organizations should immediately implement network-level protections such as strict firewall rules to restrict access to Navis N4 ULC interfaces to trusted IP addresses only. Deploying Web Application Firewalls (WAFs) with custom rules to detect and block suspicious serialized Java objects can help mitigate exploitation attempts. Organizations should conduct thorough network segmentation to isolate Navis N4 servers from general enterprise networks, limiting potential lateral movement. Monitoring and logging of all requests to the Navis N4 ULC should be enhanced to detect anomalous deserialization patterns or unexpected payloads. Additionally, organizations should engage with Kaleris for timely updates and consider temporary disabling or restricting the use of the vulnerable ULC component if operationally feasible. Implementing runtime application self-protection (RASP) or Java security managers to restrict deserialization behavior can provide additional defense layers. Finally, organizations should prepare incident response plans specific to this vulnerability, including rapid containment and forensic analysis capabilities.