CVE-2026-3611: Honeywell IQ412 Firmware

Critical severity, CVSS 10.0. EPSS: 1% chance of exploitation in the next 30 days.

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 products

• Honeywell IQ412 Firmware: before 3.30 (fixed in 3.30)
• Honeywell IQ41X Firmware: before 3.30 (fixed in 3.30)
• Honeywell IQ422 Firmware: before 3.30 (fixed in 3.30)
• Honeywell IQ4E Firmware: before 3.30 (fixed in 3.30)
• Honeywell IQ4NC Firmware: before 3.30 (fixed in 3.30)

Published 2026-03-12. Last modified 2026-06-17.