CVE-2026-21654

CriticalRCE

Published: 27 February 2026

Published

27 February 2026

Modified

02 March 2026

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0015 35.5th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-21654 is a critical-severity OS Command Injection (CWE-78) vulnerability in Johnsoncontrols Frick Controls Quantum Hd Firmware. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 35.5th 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).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Directly mitigates OS command injection by enforcing validation of untrusted inputs used in OS commands before processing.

SI-2 Flaw Remediation good match

prevent

Addresses the specific flaw in Quantum HD version 10.22 and prior through timely installation of vendor-provided security patches.

SI-9 Information Input Restrictions partial match

prevent

Complements input validation by restricting the types and quantities of inputs to prevent exploitation of command injection parameters.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1059 Command and Scripting Interpreter Execution

Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.

attack.mitre.org →

Why these techniques?

Unauthenticated remote OS command injection in a network-accessible device enables exploitation of public-facing application (T1190) and arbitrary command execution via OS command interpreter (T1059).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') vulnerability in Johnson Controls Frick Controls Quantum HD allows OS Command Injection. Insufficient validation of input in certain parameters may permit unexpected actions, which could impact the…

security of the device before authentication occurs.This issue affects Frick Controls Quantum HD version 10.22 and prior.

Deeper analysisAI

CVE-2026-21654 is an OS Command Injection vulnerability (CWE-78) affecting Johnson Controls Frick Controls Quantum HD in versions 10.22 and prior. The flaw stems from improper neutralization of special elements used in OS commands, with insufficient validation of input in certain parameters. This allows unexpected actions that impact device security even before authentication occurs. 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 critical severity.

Remote attackers require no privileges, authentication, or user interaction to exploit the issue over the network with low complexity. Successful exploitation enables arbitrary OS command execution on the affected device, potentially resulting in high-impact compromise of confidentiality, integrity, and availability, such as full system control or disruption of industrial control functions.

CISA has published ICS Advisory ICSA-26-057-01, and Johnson Controls has issued related guidance via its Trust Center cybersecurity security advisories page, detailing mitigation steps for this vulnerability.