CVE-2026-3611
Severity CVSS v4.0:
CRITICAL
Type:
CWE-306
Missing Authentication for Critical Function
Publication date:
12/03/2026
Last modified:
12/03/2026
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.
Impact
Base Score 4.0
10.00
Severity 4.0
CRITICAL
Base Score 3.x
10.00
Severity 3.x
CRITICAL