# CVE-2026-3611: Honeywell IQ4x BMS Controller Missing authentication for critical function

> Remote attackers can create admin accounts on Honeywell IQ4x controllers due to missing authentication, locking out legitimate operators.

- **Severity:** Critical 10.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Mar 2026
- **Updated:** 30 Mar 2026
- **Also known as:** GHSA-3p4g-vg78-jqrv

## What is CVE-2026-3611?

CVE-2026-3611 is a critical missing authorization vulnerability in Honeywell IQ3, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-3611?

It affects 5 products.


Products: Honeywell Iq412 Firmware, Honeywell Iq41x Firmware, Honeywell Iq422 Firmware, Honeywell Iq4e Firmware, Honeywell Iq4nc Firmware.

## How do I fix CVE-2026-3611?

No fix has been published for CVE-2026-3611 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3611 being exploited?

There is no known exploitation of CVE-2026-3611 in the wild and no public exploit code.

Public exploit code:

- Free BACnet/BMS vulnerability scanner for building automation systems. Detects CVE-2026-3611 (CVSS 10.0), CVE-2026-24060, and exposed HVAC/BAS controllers via PowerShell or Bash. (github_poc): https://github.com/spinfosecurity/BAS-Guardian

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3611 and fix it if it is affected.

What it is: CVE-2026-3611 is a critical missing authorization vulnerability in Honeywell IQ3, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-3611 in the wild and no public exploit code.

Affected product: Honeywell IQ3. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-3611/ (Markdown: https://insights.sbomify.com/CVE-2026-3611/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3611
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3611
- OSV: https://osv.dev/vulnerability/CVE-2026-3611

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3611/
Summaries are generated and may contain mistakes; the official description above is the record.