Vulnerability 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.
CVSS Score
CRITICAL
Related Weaknesses (CWE)
References
- https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-06
- https://www.cisa.gov/news-events/ics-advisories/icsa-26-069-03
- https://www.honeywell.com/us/en/contact
FAQ
What is CVE-2026-3611?
CVE-2026-3611 is a vulnerability with a CVSS score of 10.0 (CRITICAL). 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 d...
How severe is CVE-2026-3611?
CVE-2026-3611 has been rated CRITICAL with a CVSS base score of 10.0/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-3611?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.