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1. EXECUTIVE SUMMARY

• CVSS v4 6.3
• ATTENTION: Low attack complexity
• Vendor: Johnson Controls Inc.
• Equipment: iSTAR Configuration Utility (ICU) tool
• Vulnerability: Use of Uninitialized Variable

2. RISK EVALUATION

Successful exploitation of this vulnerability may allow an attacker to gain access to memory leaked from the ICU. This utility is only used to configure products that are no longer manufactured or supported. ICU is not used to configure the iSTAR Ultra and the current iSTAR G2 series of controllers. Furthermore, this vulnerability only impacts ICU and the Windows PC it is running on. This vulnerability does not impact iSTARs, including the legacy iSTARs.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

Johnson Controls reports the following versions of ICU are affected:

• ICU: All versions prior to 6.9.5

3.2 VULNERABILITY OVERVIEW

3.2.1 USE OF UNINITIALIZED VARIABLE CWE-457

The iSTAR Configuration Utility (ICU) tool leaks memory, which could result in the unintended exposure of unauthorized data from the Windows PC that ICU is running on.

CVE-2025-26383 has been assigned to this vulnerability. A CVSS v3.1 base score of 7.4 has been calculated; the CVSS vector string is (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N).

A CVSS v4 score has also been calculated for CVE-2025-26383. A base score of 6.3 has been calculated; the CVSS vector string is (CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:H/SI:N/SA:N).

3.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Commercial Facilities, Critical Manufacturing, Energy, Government Services and Facilities, Transportation Systems
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Ireland

3.4 RESEARCHER

Reid Wightman of Dragos reported this vulnerability to Johnson Controls Inc.

4. MITIGATIONS

Johnson Controls recommends users update ICU to Version 6.9.5 or greater.

For more detailed mitigation instructions, please see Johnson Controls Product Security Advisory JCI-PSA-2025-06

For assistance and additional information, please contact Johnson Controls Trust Center
trustcenter@jci.com

CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, 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.

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

5. UPDATE HISTORY

• May 27, 2025: Initial Republication of Johnson Controls security advisory