CVE-2025-26386 is a stack-based buffer overflow vulnerability identified in Johnson Controls iSTAR Configuration Utility (ICU) versions 6.9.7 and prior. The vulnerability stems from improper handling of input data that allows an attacker to overflow a buffer on the stack, leading to memory corruption. This can result in arbitrary code execution, privilege escalation, or denial of service conditions. The vulnerability is remotely exploitable over the network without requiring authentication or privileges, but it does require user interaction, such as opening a maliciously crafted configuration file or input. The CVSS v4.0 score of 7.1 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no need for privileges. The ICU tool is used primarily for configuring and managing Johnson Controls iSTAR access control systems, which are widely deployed in physical security environments including enterprise buildings, industrial facilities, and critical infrastructure. Although no public exploits are known at this time and no patches have been released, the vulnerability poses a significant risk due to the potential for attackers to gain control over security management systems. The lack of authentication requirements and network accessibility increase the attack surface. The CWE-121 classification highlights the classic buffer overflow nature of the flaw, which is a well-understood and often exploited vulnerability type. Organizations using the ICU tool should be aware of this threat and prepare mitigation strategies accordingly.

For European organizations, the impact of CVE-2025-26386 can be severe. Johnson Controls iSTAR systems are commonly used in physical access control for corporate offices, government buildings, transportation hubs, and critical infrastructure such as energy and utilities. Exploitation could allow attackers to execute arbitrary code on the configuration utility, potentially leading to unauthorized changes in access control policies, disabling of security mechanisms, or full compromise of the physical security management system. This undermines both physical and cyber security, increasing the risk of unauthorized facility access, data breaches, and operational disruptions. The vulnerability could also be leveraged as a foothold for lateral movement within enterprise networks. Given the critical nature of affected environments, successful exploitation could have cascading effects on safety, compliance, and business continuity. The absence of known exploits currently provides a window for proactive defense, but the high severity and ease of exploitation necessitate urgent attention.

1. Immediately restrict network access to the iSTAR Configuration Utility to trusted administrators and management networks only, using firewalls and network segmentation. 2. Implement strict input validation and monitoring on systems running the ICU tool to detect anomalous or malformed configuration data. 3. Educate users and administrators to avoid opening untrusted or suspicious configuration files or inputs that could trigger the overflow. 4. Monitor security advisories from Johnson Controls for patches or updates addressing this vulnerability and plan for rapid deployment once available. 5. Employ endpoint protection solutions capable of detecting buffer overflow exploitation techniques and unusual process behavior related to the ICU tool. 6. Conduct regular security audits and penetration testing focused on physical security management systems to identify potential exploitation attempts. 7. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics targeting buffer overflow attempts against the ICU tool. 8. Maintain comprehensive logging and alerting on ICU-related activities to facilitate rapid incident response. 9. If possible, isolate the ICU tool environment from general enterprise networks to limit exposure. 10. Develop and test incident response plans specific to physical security system compromises.