A researcher claims to have identified a high-risk vulnerability in a Honeywell building management controller, but the vendor disputes the severity and impact of the findings.
Cybersecurity researcher Gjoko Krstic, known in the industry for his analysis of building control systems and the discovery of high-impact vulnerabilities, recently investigated Honeywell’s IQ4 controller.
According to Krstic, the product exposes its web-based human-machine interface (HMI) without authentication in its factory-default configuration.
The researcher also found that if the product is not properly configured and a user module is not enabled during setup, a remote attacker who has access to the management interface can create an account with administrator permissions, before legitimate users set up their accounts.
“This action can effectively lock legitimate operators out of local and web-based configuration and administration,” Krstic said in an advisory published this week.
The researcher warned that the vulnerability could expose schools, commercial buildings, and other facilities that use the building control system.
The findings were reported to Honeywell in December 2025, but the vendor is apparently not releasing any patches, arguing that the IQ4 product is designed for on-premises use and should not be exposed to the internet.
“IQ4 devices are delivered unconfigured and are set up by trained technicians before they become operational,” Honeywell said in a statement to SecurityWeek. “The scenario described by the researcher could only occur during a brief installation phase, before the system is active, or if security settings were deliberately disabled against clear warnings.”
“At that stage, the device cannot monitor or control any equipment, and there is no impact on operations. Any installation issue can be resolved through a standard reset, and when installed using normal processes, security is automatically enabled as part of a secure‑by‑default design,” Honeywell added.
However, the researcher disagrees with this statement and Honeywell’s risk assessment. Krstic said he identified nearly 7,500 internet-exposed instances of the product, and an estimated 20% can be accessed without authentication.
The researcher also disputes Honeywell’s claims that the device cannot monitor or control any equipment if it’s not fully set up.
“I’ve seen installations where the user account has not been created and I was able to write changes to components like lighting and temperature, turn off the boiler or chiller, and other operations on control equipment,” Krstic told SecurityWeek.
SecurityWeek can confirm that many IQ4 interface instances are exposed to the internet, but has not verified the other claims.
Krstic said a CVE for the vulnerability is pending. The researcher recently also reached out to the CERT Coordination Center (CERT/CC) at Carnegie Mellon University, which often mediates vulnerability disclosures.
Threat actors often target building automation systems in their attacks, according to cybersecurity firms.
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