Public proof of conceptFix available

CVE-2026-3611

Q: Is CVE-2026-3611 actively exploited?

Active exploitation of CVE-2026-3611 has not been confirmed. Its EPSS score was 1.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

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

CVE-2026-3611 has a CVSS v3 base score of 10 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2026-03-12
Fixed in3.30
WeaknessCWE-306

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2026-03-1221:16CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-3611?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-3611?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Honeywell iq412 firmwareversion to verify

Branch	Affected	Fixed in	Source
3.30	< 3.30	3.30	NVD

Honeywell iq41x firmwareversion to verify

Branch	Affected	Fixed in	Source
3.30	< 3.30	3.30	NVD

Honeywell iq422 firmwareversion to verify

Branch	Affected	Fixed in	Source
3.30	< 3.30	3.30	NVD

2 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

ICSA-26-069-03 CISA5 known affected
Honeywell IQ4 Series BMS Controller (Update A)
Honeywell IQ4E Firmware: <v3.30 · Honeywell IQ412 Firmware: <v3.30 · Honeywell IQ422 Firmware: <v3.30 · +2 more

Full record on NVD

Fix

Update Honeywell iq412 firmware to 3.30
Mitigation from the vendor CISA ICSA-26-069-03 · 5 productsVersion 3.30, released June 2015, and later force users to install a user module upon the commissioning of the device. This user module enables authentication and other security features for the web interface. When updating previously commissioned devices to firmware versions 3.30 or later (current…
Mitigation from the vendor CISA ICSA-26-069-03 · 5 productsHoneywell recommends that users with affected products take the following steps:
Mitigation from the vendor CISA ICSA-26-069-03 · 5 productsApply product updates as available.
Mitigation from the vendor CISA ICSA-26-069-03 · 5 productsFollow guidance in the product security manual to ensure isolation of network segments hosting building automation controllers.
Mitigation from the vendor CISA ICSA-26-069-03 · 5 productsEnsure adequate security controls are in place between OT and IT segments.
Mitigation from the vendor CISA ICSA-26-069-03 · 5 productsDisable unnecessary accounts and services.

Detection

read 2026-10-23 19:25 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedspinfosecurity/BAS-Guardian

Sources

CISA-ADPSSVC decisionnone2026-03-13
OpenCVESSVC decisionnone—
CNACVSS 4.010read 2026-10-23
CNACVSS 3.110read 2026-10-23
NVDCVSS 3.110read 2026-10-23
CNAweakness (CWE)CWE-306read 2026-10-23
FIRST EPSSEPSS score1.0 %2026-10-23
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CVSS 4.0 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
Published: 2026-03-12
Last Modified: 2026-06-17
NVD status: Analyzed

Frequently asked questions

What is CVE-2026-3611?

Is CVE-2026-3611 actively exploited?

Active exploitation of CVE-2026-3611 has not been confirmed. Its EPSS score was 1.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-3611?

CVE-2026-3611 has a CVSS v3 base score of 10 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

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