CVE-2025-2566: Kaleris NAVIS N4 ULC RCE Vulnerability

CVE-2025-2566 Overview

CVE-2025-2566 is a critical unsafe Java deserialization vulnerability affecting Kaleris NAVIS N4 ULC (Ultra Light Client). This insecure deserialization flaw allows an unauthenticated attacker to craft malicious requests that exploit the Java deserialization mechanism, ultimately leading to arbitrary code execution on the target server. The vulnerability requires no authentication, making it particularly dangerous in exposed environments.

Critical Impact

Unauthenticated remote code execution via unsafe Java deserialization in Kaleris NAVIS N4 ULC allows attackers to fully compromise server infrastructure without any credentials.

Affected Products

• Kaleris NAVIS N4 ULC (Ultra Light Client)

Discovery Timeline

• 2025-06-24 - CVE-2025-2566 published to NVD
• 2025-06-26 - Last updated in NVD database

Technical Details for CVE-2025-2566

Vulnerability Analysis

This vulnerability is classified under CWE-502 (Deserialization of Untrusted Data). Java deserialization vulnerabilities occur when an application deserializes data from untrusted sources without proper validation. In the context of NAVIS N4 ULC, the application processes serialized Java objects from network requests without adequately verifying the integrity or safety of the incoming data.

When a Java application deserializes an object, it reconstructs the object in memory based on the serialized byte stream. Attackers can exploit this by crafting malicious serialized objects that, when deserialized, trigger dangerous operations such as executing system commands or loading malicious classes. This attack surface is network-accessible and requires no prior authentication, significantly increasing the risk profile.

The NAVIS N4 platform is commonly used in port and terminal operations for managing container logistics. Compromise of such systems could have cascading effects on critical infrastructure operations, supply chain visibility, and operational continuity.

Root Cause

The root cause of CVE-2025-2566 is the unsafe handling of Java serialized objects received from untrusted network sources. The NAVIS N4 ULC component fails to implement proper deserialization filters or input validation, allowing attackers to inject malicious serialized payloads. When the application processes these payloads using Java's ObjectInputStream without restrictions, it instantiates attacker-controlled objects that can execute arbitrary code during the deserialization lifecycle through methods like readObject() or readResolve().

Attack Vector

The attack is conducted over the network without requiring authentication. An attacker sends a specially crafted HTTP request containing a malicious serialized Java object to the NAVIS N4 ULC endpoint. The server-side application deserializes the payload, triggering the execution of arbitrary code embedded within the malicious object graph.

Typical attack chains leverage publicly known "gadget chains" from common Java libraries present in the application's classpath. These gadget chains abuse legitimate class functionality to achieve code execution when combined in specific serialization patterns. Tools like ysoserial are commonly used to generate such payloads.

The vulnerability can be exploited by constructing a serialized Java object containing a malicious gadget chain. When the NAVIS N4 ULC server deserializes the attacker-controlled payload, the gadget chain executes arbitrary system commands with the privileges of the application server. For detailed technical information, refer to the CISA ICS Advisory ICSA-25-175-01.

Detection Methods for CVE-2025-2566

Indicators of Compromise

• Unusual outbound network connections from NAVIS N4 ULC server processes to unknown external IP addresses
• Presence of suspicious processes spawned by the Java application server (e.g., cmd.exe, powershell.exe, /bin/sh, /bin/bash)
• HTTP requests containing serialized Java object signatures (aced 0005 magic bytes or Base64-encoded equivalents)
• Unexpected file system modifications in application directories or system paths
• Authentication bypass attempts or requests to endpoints without proper session tokens

Detection Strategies

• Monitor network traffic for Java serialization magic bytes (AC ED 00 05) in HTTP request bodies targeting NAVIS N4 ULC endpoints
• Deploy web application firewalls (WAF) with rules to detect and block serialized Java object payloads
• Implement endpoint detection rules to identify child processes spawned by the NAVIS N4 application server
• Review application logs for deserialization exceptions or unusual error patterns that may indicate exploitation attempts

Monitoring Recommendations

• Enable verbose logging on NAVIS N4 ULC servers to capture detailed request information
• Configure SIEM alerts for process creation events involving the Java runtime spawning shell processes
• Monitor for file integrity changes in application and system directories
• Establish baseline network behavior and alert on anomalous outbound connections from the application server

How to Mitigate CVE-2025-2566

Immediate Actions Required

• Restrict network access to NAVIS N4 ULC endpoints using firewall rules to limit exposure to trusted networks only
• Implement network segmentation to isolate the NAVIS N4 infrastructure from general network access
• Deploy web application firewall rules to detect and block serialized Java payloads
• Review and audit current access to NAVIS N4 ULC servers for unauthorized connections
• Contact Kaleris for vendor-specific remediation guidance and patch availability

Patch Information

Organizations should consult the CISA ICS Advisory ICSA-25-175-01 for the latest remediation guidance and contact Kaleris directly for patched versions of NAVIS N4 ULC. Apply vendor-supplied security updates as soon as they become available.

Workarounds

• Implement strict network access controls limiting connectivity to NAVIS N4 ULC to authorized IP ranges only
• Deploy Java deserialization filters using ObjectInputFilter if the application runtime supports it (Java 9+ or backported to Java 8u121+)
• Remove unnecessary gadget libraries from the application classpath where possible to reduce attack surface
• Consider deploying runtime application self-protection (RASP) solutions to detect and block deserialization attacks

# Example: Restrict network access to NAVIS N4 ULC using iptables
# Allow only specific trusted IP ranges to access the application port
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP