CVE-2026-21658

CriticalRCE

Published: 27 February 2026

Published

27 February 2026

Modified

02 March 2026

KEV Added

—

Patch

—

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 0.0037 59.2th percentile

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

Summary

CVE-2026-21658 is a critical-severity Code Injection (CWE-94) 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 in the top 40.8% of CVEs by exploit likelihood; 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). 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 the code injection vulnerability by requiring comprehensive input validation at affected parameters to prevent unexpected code execution.

SI-2 Flaw Remediation good match

prevent

Ensures timely patching and remediation of the specific unauthenticated RCE flaw in Quantum HD version 10.22 and prior, as outlined in vendor advisories.

AC-14 Permitted Actions Without Identification or Authentication partial match

prevent

Limits and documents permitted unauthenticated actions to prohibit those enabling code injection and security impacts prior to authentication.

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 →

Why these techniques?

The vulnerability is an unauthenticated remote code execution in a network-accessible industrial control system device via code injection in parameters, directly enabling exploitation of a public-facing application.

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

NVD Description

Unauthenticated Remote Code Execution i.e 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 occurs.This issue affects Frick Controls Quantum HD version 10.22 and prior.

Deeper analysisAI

CVE-2026-21658 is an unauthenticated remote code execution vulnerability stemming from improper control of code generation, classified as a code injection issue (CWE-94), in Johnson Controls Frick Controls Quantum HD. The flaw arises from insufficient validation of input in certain parameters, enabling unexpected actions that compromise device security prior to authentication. It affects Quantum HD version 10.22 and prior versions, earning 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).

Attackers require no privileges or user interaction and can exploit the vulnerability remotely over the network with low complexity. Successful exploitation grants full remote code execution, potentially allowing high-impact disruption to confidentiality, integrity, and availability of the affected device.

Mitigation details are outlined in the CISA ICS advisory ICSA-26-057-01 and Johnson Controls security advisories, available at the respective reference URLs. Security practitioners should consult these for patching instructions and workarounds.