CVE-2026-3611

Summary

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 Software

Weaknesses

• CWE-306: CWE-306 Missing authentication for critical function

Workarounds

Honeywell is aware of the issue, but has not released a fix. For more information, contact Honeywell directly. https://www.honeywell.com/us/en/contact.

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: total

References

• https://www.cisa.gov/news-events/ics-advisories/icsa-26-069-03
• https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-069-03.json
• https://www.honeywell.com/us/en/contact

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