Summary
Successful exploitation of this vulnerability could allow an unauthorized attacker to access controller management settings, control components, disclose information, or cause a denial-of-service condition.
The following versions of Honeywell IQ4x BMS Controller are affected:
- IQ4E >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
- IQ412 >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
- IQ422 >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
- IQ4NC >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
- IQ41x >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
- IQ3 >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
- IQECO >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9 (CVE-2026-3611)
| CVSS | Vendor | Equipment | Vulnerabilities |
|---|---|---|---|
| v3 10 | Honeywell | Honeywell IQ4x BMS Controller | Missing Authentication for Critical Function |
Background
- Critical Infrastructure Sectors: Commercial Facilities, Critical Manufacturing, Government Services and Facilities, Healthcare and Public Health
- Countries/Areas Deployed: Worldwide
- Company Headquarters Location: United States
Vulnerabilities
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.
Affected Products
Honeywell IQ4x BMS Controller
Honeywell
Honeywell IQ4E: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9, Honeywell IQ412: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9, Honeywell IQ422: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9, Honeywell IQ4NC: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9, Honeywell IQ41x: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9, Honeywell IQ3: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9, Honeywell IQECO: >=Firmware_v3.50_3.44|<4.36_build_4.3.7.9
known_affected
Remediations
Mitigation
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.
Relevant CWE: CWE-306 Missing Authentication for Critical Function
Metrics
| CVSS Version | Base Score | Base Severity | Vector String |
|---|---|---|---|
| 3.1 | 10 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
Acknowledgments
- Gjoko Krstic of Zero Science reported this vulnerability to Honeywell
Legal Notice and Terms of Use
This product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy).
Recommended Practices
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, such as:
Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet.
Locate control system networks and remote devices behind firewalls and isolating them from business networks.
When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.
CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.
Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B–Targeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.
CISA also recommends users take the following measures to protect themselves from social engineering attacks:
Do not click web links or open attachments in unsolicited email messages.
Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams.
Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks.
No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time.
Revision History
- Initial Release Date: 2026-03-10
| Date | Revision | Summary |
|---|---|---|
| 2026-03-10 | 1 | Initial Publication |
