IQ4E: Missing Authentication for Critical Functionality
CVE-2026-3611 is a critical-severity missing authentication for critical functionality vulnerability in IQ4E from Honeywell, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected IQ4E versions: v3.50_3.44 through 4.36 (build 4.3.7.9). The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 6.3% chance of exploitation within 30 days, which is in the top 6.29% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Iq4e Firmware to 3.30 or a later version.
- Update Iq412 Firmware to 3.30 or a later version.
- Update Iq422 Firmware to 3.30 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Honeywell | IQ4E | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | IQ412 | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | IQ422 | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | IQ4NC | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | IQ41x | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | IQ3 | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | IQECO | v3.50_3.44 through 4.36 (build 4.3.7.9) | Not stated |
| Honeywell | Iq4e Firmware | before 3.30 | 3.30 |
| Honeywell | Iq412 Firmware | before 3.30 | 3.30 |
| Honeywell | Iq422 Firmware | before 3.30 | 3.30 |
| Honeywell | Iq4nc Firmware | before 3.30 | 3.30 |
| Honeywell | Iq41x Firmware | before 3.30 | 3.30 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 10.0 | Critical | CNA (hq.dhs.gov) |
| CVSS 3.1 | 10.0 | Critical | CNA (hq.dhs.gov) |
| CVSS 3.1 | 10.0 | Critical | NVD |
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Missing Authentication for Critical Functionality
The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
How developers prevent this class of flaw
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using libraries with authentication capabilities such as OpenSSL or the ESAPI Authenticator.
- When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to require strong authentication for users who should be allowed to access the data.
More Missing Authentication for Critical Functionality vulnerabilities (CWE-306)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/news-events/ics-advisories/icsa-26-069-03Third Party Advisory, US Government Resource
Other references
Recent Missing Authentication for Critical Functionality vulnerabilities
- 8.2 High severity
- 9.8 Critical severity
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.5 High severity
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