CVE-2026-3611: Honeywell IQ4x BMS Controller Missing authentication for critical function

DescriptionCVE.org

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 · IQ4Efrom v3.50_3.44 up to and including 4.36 (build 4.3.7.9)
• Honeywell · IQ412from v3.50_3.44 up to and including 4.36 (build 4.3.7.9)
• Honeywell · IQ422from v3.50_3.44 up to and including 4.36 (build 4.3.7.9)
• Honeywell · IQ4NCfrom v3.50_3.44 up to and including 4.36 (build 4.3.7.9)
• Honeywell · IQ41xfrom v3.50_3.44 up to and including 4.36 (build 4.3.7.9)
• Honeywell · IQ3from v3.50_3.44 up to and including 4.36 (build 4.3.7.9)
• Honeywell · IQECOfrom v3.50_3.44 up to and including 4.36 (build 4.3.7.9)

Exploitation

Possible (1 to 10%). EPSS between 1% and 10%.

CISA KEV

Not listed

Public check

No public nuclei template

Weakness

Missing Authentication · Authentication

Vendor

Honeywell

Published

March 2026

Band

Possible (1 to 10%), March 2026

• NVD entrynvd.nist.gov
• CVE recordcve.org
• Weakness CWE-306cwe.mitre.org
• cisa.gov/news-events/ics-advisories/icsa-26-069-03cisa.gov
• github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icgithub.com
• honeywell.com/us/en/contacthoneywell.com