CVE-2026-3611
CRITICALCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
2Description
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.
Analysis
Unauthenticated access to Honeywell IQ4x building controller HMI. CVSS 10.0.
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Remediation
Within 24 hours: Audit your environment to identify all Honeywell IQ4x devices and isolate them to restricted network segments; document findings and notify facilities/operations leadership. Within 7 days: Implement network access controls (firewall rules, VLANs) to restrict HMI access to authorized personnel only; change all default credentials; deploy network monitoring on these systems. …
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External POC / Exploit Code
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