CVE-2026-3611: The Honeywell IQ4x building management controller, exposes its full web-based HMI without authentication in its factory-default configuration. With no user…

PriorityP278critical10CVSS 3.1

AVNACLPRNUINSCCHIHAH

EPSS

5.58%

91.9th percentile

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.

Affected

12 ranges

Vendor	Product	Version range	Fixed in
honeywell	iq3	v3.50_3.44 – 4.36 (build 4.3.7.9)	—
honeywell	iq412	v3.50_3.44 – 4.36 (build 4.3.7.9)	—
honeywell	iq412_firmware	< 3.30	3.30
honeywell	iq41x	v3.50_3.44 – 4.36 (build 4.3.7.9)	—
honeywell	iq41x_firmware	< 3.30	3.30
honeywell	iq422	v3.50_3.44 – 4.36 (build 4.3.7.9)	—
honeywell	iq422_firmware	< 3.30	3.30
honeywell	iq4e	v3.50_3.44 – 4.36 (build 4.3.7.9)	—
honeywell	iq4e_firmware	< 3.30	3.30
honeywell	iq4nc	v3.50_3.44 – 4.36 (build 4.3.7.9)	—
honeywell	iq4nc_firmware	< 3.30	3.30
honeywell	iqeco	v3.50_3.44 – 4.36 (build 4.3.7.9)	—

CVSS provenance

nvdv3.110.0CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

nvdv4.010.0CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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