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CVE-2026-3611: The Honeywell IQ4x building management controller, exposes its full web-based HMI without authentication in it

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CRITICAL 10.0REMOTEUPGRADEUPGRADEUPGRADE

CVE-2026-3611 is a critical-severity flaw (CVSS 10.0) affecting iq4e firmware, iq412 firmware, iq422 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Honeywell IQ4x building management controller, exposes its full web-based HMI without authentication in its factory-default configuration. With no user module configured, security is disabled by design and the system operates under a System Guest (level 100) context, granting read/write privileges to any party able to reach the HTTP interface. Authentication controls are only enforced after a web user is created via U.htm, which dynamically e

Why this priority

  • Critical severity
  • EPSS top 7%: very likely to be exploited
  • CISA SSVC: automatable with total technical impact
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score10.0 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance5.6% (top 7%)
CISA exploited listNo
WeaknessCWE-306
Published2026-03-12
Last modified2026-06-17
Publisher (CNA): ICS-CERT · Vendor: honeywell

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

honeywell iq4e firmware UPGRADE
Affected: < 3.30
Fixed in: 3.30
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
honeywell iq412 firmware UPGRADE
Affected: < 3.30
Fixed in: 3.30
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
honeywell iq422 firmware UPGRADE
Affected: < 3.30
Fixed in: 3.30
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
honeywell iq4nc firmware UPGRADE
Affected: < 3.30
Fixed in: 3.30
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
honeywell iq41x firmware UPGRADE
Affected: < 3.30
Fixed in: 3.30
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

Fedora ELN · fonttools · FIXED · 4.68.0-1.eln159 · FEDORA-2026-37fa4b964c · source
sudo dnf upgrade --advisory=FEDORA-2026-37fa4b964c
Fedora 46 · fonttools · FIXED · 4.68.0-1.fc46 · FEDORA-2026-65d6c01c75 · source
sudo dnf upgrade --advisory=FEDORA-2026-65d6c01c75

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-3611?

iq4e firmware: upgrade to 3.30; iq412 firmware: upgrade to 3.30; iq422 firmware: upgrade to 3.30. Exact commands for each OS are on this page.

Is CVE-2026-3611 being exploited?

CVE-2026-3611 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-3611 affect?

CVE-2026-3611 affects iq4e firmware, iq412 firmware, iq422 firmware. Severity is critical (CVSS 10.0). The Honeywell IQ4x building management controller, exposes its full web-based HMI without authentication in its factory-default configuration. With no user module configured, security is disabled by design and the system operates under a Sy

How urgent is CVE-2026-3611?

Priority 66/100. Critical severity; EPSS top 7%: very likely to be exploited; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

Honeywell vulnerabilities

References

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