Which versions of Honeywell are affected by CVE-2026-3611?

Honeywell IQ4x building management controllers in their default configuration expose critical infrastructure control interfaces without any authentication, allowing unauthorized remote access to…

How to fix or mitigate CVE-2026-3611?

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. Within 30 days: Evaluate vendor guidance for configuration hardening; consider replacing or retiring affected devices if no acceptable mitigation path emerges; implement continuous vulnerability scanning for similar exposures.

Honeywell CVE-2026-3611

Q: What is the CVSS score of CVE-2026-3611?

CVE-2026-3611 has a CVSS 4.0 base score of 10.0 (Critical). CVSS vector: CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.1%.

CRITICAL

Missing Authentication for Critical Function (CWE-306)

2026-03-12 ics-cert@hq.dhs.gov

Authentication Bypass Honeywell

10.0

CVSS 4.0 · NVD

Severity by source

NVD PRIMARY

10.0 CRITICAL

CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:55 vuln.today

CVE Published

Mar 12, 2026 - 21:16 nvd

CRITICAL 10.0

DescriptionCVE.org

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.