What is the CVSS score of CVE-2026-21656?

CVE-2026-21656 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.1%.

How to fix or mitigate CVE-2026-21656?

Within 24 hours: Inventory all Frick Controls Quantum HD deployments and assess network exposure; immediately isolate affected systems or restrict network access to trusted administrators only. Within 7 days: Implement compensating controls including network segmentation, WAF rules blocking suspicious input patterns, and enhanced monitoring for exploitation attempts. Within 30 days: Establish vendor communication cadence for patch availability; evaluate alternative control solutions and develop incident response procedures specific to this vulnerability.

Frick Controls Quantum Hd Firmware CVE-2026-21656

CRITICAL

Code Injection (CWE-94)

2026-02-27 productsecurity@jci.com

Code Injection Frick Controls Quantum Hd Firmware Johnsoncontrols

9.8

CVSS 3.1 · NVD

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Send crafted network request with malicious code
Exploit

Bypass input validation in parameter processing
Execution

Inject executable code
Impact

Execute arbitrary commands pre-authentication

Vulnerability Assessment

Weakness	CWE CWE-94 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Code injection prevention, sandbox exec MITRE ATT&CK 2 techniques across 2 tactics: Execution, Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Exploitation Conditions	Frick Controls Quantum HD version 10.22 or earlier must be accessible over network with unvalidated input parameters. No authentication required; vulnerability exists in pre-authentication code path.
Impact	CVSS 9.8. Multiple attack vectors increase exploitation likelihood for this ICS product.
Exploit ScenarioDerived	Attacker injects code through a different interface than the command injection CVE, achieving arbitrary code execution on the refrigeration controller.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Code injection in Johnson Controls Frick Controls Quantum HD allows unauthenticated remote code execution on industrial refrigeration systems. Second critical vulnerability in the Quantum HD product line.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 21:55 CVSS 9.8

Code injection in Johnson Controls Frick Quantum HD — second CVE.

RemediationAI

Apply vendor patches for all Frick Quantum HD CVEs. Network-isolate industrial controllers.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

CWE-94 code injection. Different attack vector from CVE-2026-21654 but same product and impact — unauthenticated RCE on refrigeration controllers.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionCVE.org

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.

Executive ViewAI

Why It Matters

A critical code injection vulnerability (CVSS 9.8) affects Johnson Controls Frick Controls Quantum HD systems, allowing attackers to execute arbitrary code and potentially gain full system control. Organizations using this HVAC control platform face immediate risk of operational disruption, data breach, and facility compromise, with no vendor patch currently available.

Business Impact: Severe

Compensating Controls

Network segmentation to restrict unauthorized access to Quantum HD systems; implement Web Application Firewall (WAF) rules to filter code injection payloads (monitor for shell metacharacters and script injection patterns in input fields); disable remote management features if not operationally required; enforce multi-factor authentication for administrative access; deploy intrusion detection/prevention systems (IDS/IPS) with signatures for Quantum HD exploitation attempts; maintain enhanced logging and real-time alerting for suspicious activity; consider deploying an application-level gateway or reverse proxy with input validation; establish air-gapped backups of critical control configurations.

Threat Intelligence Overview

EPSS Score

0.1%

Top 74% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC No

EPSS 0.1%

Patch available No

Active threat No

Deciding rule

CRITICAL severity

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Out-of-Cycle

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Very High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +49

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Code Injection CRITICAL

Code injection occurs when an application accepts user input and passes it directly into a language interpreter or evaluator without proper sanitization.