CVE-2026-21656
Published: 27 February 2026
Summary
CVE-2026-21656 is a high-severity Code Injection (CWE-94) vulnerability in Johnsoncontrols Frick Controls Quantum Hd Firmware. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 31.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-21656 is an Improper Control of Generation of Code ('Code Injection') vulnerability, classified under CWE-94, in Johnson Controls Frick Controls Quantum HD. The flaw arises from insufficient validation of input in certain parameters, enabling code injection that can perform unexpected actions and impact device security before authentication occurs. This issue affects Frick Controls Quantum HD version 10.22 and prior versions.
The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating it is exploitable over the network with low attack complexity, no privileges or user interaction required, and unchanged impact scope. Unauthenticated remote attackers can leverage it to inject code, achieving high impacts on confidentiality, integrity, and availability of the affected device.
Advisories from CISA (ICSA-26-057-01) and Johnson Controls' trust center cybersecurity security advisories provide guidance on mitigation. Security practitioners should review these references for details on available patches, workarounds, or other protective measures.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9011
Vulnerability details
Improper Control of Generation of Code ('Code Injection') vulnerability in Johnson Controls Frick Controls Quantum HD allows Code Injection. Insufficient validation of input in certain parameters may permit unexpected actions, which could impact the security of the device before authentication…
more
occurs.This issue affects Frick Controls Quantum HD version 10.22 and prior.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability allows unauthenticated remote code injection over the network in a public-facing device application, directly mapping to exploitation of public-facing applications.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly addresses the insufficient input validation causing code injection by requiring checks at input points to prevent malicious code execution.
Mandates timely remediation of the known code injection flaw in Quantum HD version 10.22 and prior via patching as advised by CISA and Johnson Controls.
Limits permitted actions without authentication, mitigating pre-authentication code injection impacts by restricting unauthenticated input processing.