CVE-2026-3611
The Honeywell IQ4x building management controller, exposes its full web-based HMI without authentication in its factory-default configuration.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (5.50%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 4.0
- 10.0 CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 5.50% probability · 92th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-306
- Affected
- honeywell/iq4e firmware · honeywell/iq412 firmware · honeywell/iq422 firmware · honeywell/iq4nc firmware · honeywell/iq41x firmware
- Source
- ics-cert@hq.dhs.gov
References
- https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-069-03.jsonIssue Tracking
- https://www.cisa.gov/news-events/ics-advisories/icsa-26-069-03Third Party Advisory, US Government Resource
- https://www.honeywell.com/us/en/contactProduct
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.