CVE-2026-3611
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe 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 enables the user module. Because this function is accessible prior to authentication, a remote user can create a new account with administrative read/write permissions enabling the user module and imposing authentication under attacker-controlled credentials. This action can effectively lock legitimate operators out of local and web-based configuration and administration.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe Honeywell IQ4x building management controller exposes its full web-based HMI without authentication in factory-default configuration. The system operates under a System Guest (level 100) context with read/write privileges when no user module is configured. Because the U.htm user creation function is accessible prior to authentication, an unauthenticated remote attacker can create an administrative account, enabling the user module under attacker-controlled credentials and locking out legitimate operators.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 3.30< 3.30< 3.30< 3.30< 3.30CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify device model and firmware versionAccess the device web interface or query via SNMP/serial console. Look for firmware version information typically displayed on the main login page or in system settings/about section.Affected if Device model is Iq4e, Iq412, Iq422, Iq4nc, or Iq41x AND firmware version is less than 3.30
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Verify web HMI is accessible without authenticationAttempt to access the device web interface (default HTTP port 80 or 443) from an external IP address without providing any credentials. Observe if the full HMI loads without a login prompt.Affected if Full web HMI loads without requiring any authentication credentials
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Test U.htm user creation endpoint accessibilityNavigate directly to the U.htm endpoint (e.g., http://[device IP]/U.htm) without being logged in. Observe if the user creation form is displayed and functional.Affected if U.htm page loads and allows user account creation without prior authentication
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Check if user module is configuredAfter accessing U.htm or the main HMI, check if any user accounts are configured in the user management section. Look for the presence of user accounts versus a default factory state with no users defined.Affected if No user accounts are configured and the system operates in factory-default configuration with System Guest (level 100) context active
A device is affected if it is an Iq4e, Iq412, Iq422, Iq4nc, or Iq41x model with firmware below 3.30 AND the web HMI is accessible without authentication AND U.htm allows user creation without being logged in.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped3.30
Immediately network-segment the affected devices behind firewalls or place them in isolated VLANs to limit unauthorized access. Contact Honeywell for a firmware update that enforces authentication by default or implement compensating controls such as strict access control lists.
Firmware version 3.30 or later for Iq4e, Iq412, Iq422, Iq4nc, and Iq41x controllers
- 1. Obtain the official firmware upgrade package version 3.30 or later from Honeywell's official support channels (www.honeywell.com)
- 2. Review Honeywell's official upgrade instructions and release notes for any specific prerequisites
- 3. Create a full backup of the current device configuration before proceeding
- 4. Ensure the device has stable power and network connectivity during the upgrade process
- 5. Upload and apply firmware version 3.30 or later via the device's firmware update mechanism
- 6. After upgrade, verify that authentication is properly enforced by attempting to access the HMI without credentials
- 7. Immediately create an administrative user account before exposing the device to untrusted networks
- 8. If the device was previously compromised (attacker created unauthorized accounts), perform a factory reset before upgrading and then apply the new firmware
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-3611 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-3611 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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