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 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.

Honeywell iq4e Firmware

< 3.30

CVSS 3.1

10.0 CRITICAL

EPSS

5.5% (92th percentile)

Weakness

CWE-306

NVD status

Analyzed

Published

2026-03-12