CVE-2026-21654 is an OS Command Injection vulnerability classified under CWE-78 found in Johnson Controls Frick Controls Quantum HD, a building management system product widely used for HVAC and environmental control. The vulnerability exists due to improper neutralization of special elements in OS commands, which allows an attacker to inject and execute arbitrary operating system commands remotely. This flaw affects all versions up to and including 10.22. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N) indicates network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality and integrity. Although no public exploits have been reported yet, the nature of OS command injection vulnerabilities typically allows attackers to gain full control over the affected system, potentially leading to data breaches, unauthorized control of building systems, or disruption of critical infrastructure operations. The lack of available patches at the time of disclosure necessitates immediate mitigation through compensating controls. This vulnerability highlights the importance of secure coding practices, especially input validation and command sanitization in embedded and industrial control systems.

The impact of CVE-2026-21654 is significant for organizations relying on Johnson Controls Frick Controls Quantum HD for building and environmental management. Successful exploitation can lead to full system compromise, allowing attackers to execute arbitrary commands, potentially disrupting HVAC systems, causing physical damage, or impacting occupant safety and comfort. Confidentiality breaches may occur if sensitive operational data is accessed or exfiltrated. Integrity of system configurations and logs can be compromised, hindering incident response and forensic investigations. Availability may also be affected if critical control functions are disabled or manipulated. Given the critical role of building management systems in commercial, industrial, and critical infrastructure environments, this vulnerability poses risks to operational continuity and safety. The ease of exploitation without authentication or user interaction further elevates the threat level, making it attractive for attackers targeting industrial control systems or facilities management.

1. Monitor Johnson Controls communications closely for official patches or updates addressing CVE-2026-21654 and apply them promptly once available. 2. Implement network segmentation to isolate Frick Controls Quantum HD systems from general enterprise networks and restrict access to trusted administrators only. 3. Deploy strict input validation and command filtering at network boundaries or via application-layer firewalls to detect and block suspicious command injection attempts. 4. Use intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous command execution patterns related to this product. 5. Conduct regular security audits and vulnerability assessments on building management systems to identify and remediate insecure configurations. 6. Limit exposure by disabling unnecessary services and interfaces on affected devices. 7. Maintain comprehensive logging and monitoring to detect early signs of exploitation attempts. 8. Train operational technology (OT) and IT staff on this vulnerability and incident response procedures specific to building management systems. These measures, combined with patching, will reduce the attack surface and mitigate exploitation risk effectively.