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 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.

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Advisories

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Fixes

Solution

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Workaround

Honeywell is aware of the issue, but has not released a fix. For more information, contact Honeywell directly. [https://www.honeywell.com/us/en/contact](https://www.honeywell.com/us/en/contact).

History

Thu, 12 Mar 2026 20:30:00 +0000

Type Values Removed Values Added
Description 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 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.
Title Honeywell IQ4x BMS Controller Missing authentication for critical function
Weaknesses CWE-306
References
Metrics cvssV3_1

{'score': 10, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H'}

cvssV4_0

{'score': 10, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: icscert

Published:

Updated: 2026-03-12T20:06:05.753Z

Reserved: 2026-03-05T18:12:38.425Z

Link: CVE-2026-3611

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-03-12T21:16:27.693

Modified: 2026-03-12T21:16:27.693

Link: CVE-2026-3611

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses