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1. EXECUTIVE SUMMARY

• CVSS v4 9.3
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Kaleris
• Equipment: Navis N4
• Vulnerabilities: Deserialization of Untrusted Data, Cleartext Transmission of Sensitive Information

2. RISK EVALUATION

Successful exploitation of these vulnerabilities could allow an attacker to remotely exploit the operating system, achieve remote code execution, or extract sensitive information.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following versions of Kaleris Navis N4, a terminal operating system, are affected:

• Navis N4: Versions prior to 4.0

3.2 VULNERABILITY OVERVIEW

3.2.1 DESERIALIZATION OF UNTRUSTED DATA CWE-502

Kaleris NAVIS N4 ULC (Ultra Light Client) contains an unsafe Java deserialization vulnerability. An unauthenticated attacker can make specially crafted requests to execute arbitrary code on the server.

CVE-2025-2566 has been assigned to this vulnerability. A CVSS v3.1 base score of 9.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

A CVSS v4 score has also been calculated for CVE-2025-2566. A base score of 9.3 has been calculated; the CVSS vector string is (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N).

3.2.2 CLEARTEXT TRANSMISSION OF SENSITIVE INFORMATION CWE-319

Kaleris NAVIS N4 ULC (Ultra Light Client) communicates insecurely using zlib-compressed data over HTTP. An attacker capable of observing network traffic between Ultra Light Clients and N4 servers can extract sensitive information, including plaintext credentials.

CVE-2025-5087 has been assigned to this vulnerability. A CVSS v3.1 base score of 5.9 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N).

A CVSS v4 score has also been calculated for CVE-2025-5087. A base score of 6.0 has been calculated; the CVSS vector string is (AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N).

3.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Transportation Systems
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: United States

3.4 RESEARCHER

Kaleris reported these vulnerabilities to CISA.

4. MITIGATIONS

Kaleris recommends users to implement the following versions or later:

• Navis N4: Version 3.1.44+
• Navis N4: Version 3.2.26+
• Navis N4: Version 3.3.27+
• Navis N4: Version 3.4.25+
• Navis N4: Version 3.5.18+
• Navis N4: Version 3.6.14+
• Navis N4: Version 3.7.0+
• Navis N4: Version 3.8.0+

If users are unable to update, Kaleris recommends following these mitigations:

• If N4 does not need to be exposed to the internet, placing it behind a firewall.
• If CAP needs to be exposed to the internet, disable the Ultra Light Client on the nodes being exposed. This can be done by blocking the Ultra Light Client URLs in the load balancer or firewall by blocking the following patterns: "url-pattern*.jnlp</url-pattern" and "url-pattern/ulc</url-pattern"
• The Ultra Light Client endpoint can also be disabled on the N4 Cluster node by commenting out relevant code in the web.xml file and restarting the server.
• If the Ultra Light Client must be exposed to the Internet, do one of the following:
  a. Set up a secure VPN connection to allow access for known external parties.
  b. Set up an authenticated jump system (Citrix, VDI, Etc.).
  c. Whitelist external allowed IPs. (least secure option)
• Additionally, the following controls should be applied:
  a. Restrict the number of N4 nodes exposed to the internet.
  b. Ensure that HTTPS is enabled and configured on the filewall/loadbalancer.
  c. Use a reliable third-party party firewall with built in DDOS protection that can detect unwanted intrusions.
• Users are required to implement TLS in their load balancer. The setup for this is included in the Application Security Guide that is provided to all users.
• A final option to consider is upgrading to N4 4.0, where the Ultra Light Client has been fully replaced with the HTML UI.

Kaleris has sent a security advisory to all customers running Kaleris software.

For more information, users should email security@kaleris.com

CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities, such as:

• Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet.
• Locate control system networks and remote devices behind firewalls and isolating them from business networks.
• When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.

CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.

Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.

Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.

CISA also recommends users take the following measures to protect themselves from social engineering attacks:

• Do not click web links or open attachments in unsolicited email messages.
• Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams.
• Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks.

No known public exploitation specifically targeting these vulnerabilities has been reported to CISA at this time.

5. UPDATE HISTORY

• June 24, 2025: Initial Publication