CVE-2026-3611

CVE-2026-3611 is a critical-severity vulnerability in Honeywell Iq4e Firmware with a CVSS 3.x base score of 10.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-306.

Key facts

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.

Frequently asked questions

What is CVE-2026-3611?
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.
How severe is CVE-2026-3611?
CVE-2026-3611 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-3611 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3611?
CVE-2026-3611 primarily affects Honeywell Iq4e Firmware. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-3611?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-3611 have an EU (EUVD) identifier?
Yes. CVE-2026-3611 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11706.
When was CVE-2026-3611 published?
CVE-2026-3611 was published on 2026-03-12 and last updated on 2026-06-17.

References

Affected products (5)

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