---
title: "CVE-2023-4346: KNX Association KNX Protocol Connection Authorization Option 1 Overly Restrictive Account Lockout Mechanism Vulnerability"
url: https://erroneo.us/security/cve/CVE-2023-4346/
description: "CVE-2023-4346 (KNX Association KNX Protocol Connection Authorization Option 1): Exploited in the wild (CISA KEV). KNX devices that use KNX Connection…"
type: vulnerability-record
section: "Security Digest"
date_published: 2023-08-29
date_modified: 2026-07-16
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2023-4346"
kev: true
cvss: 7.5
epss: 0.01294
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2023-4346: KNX Association KNX Protocol Connection Authorization Option 1 Overly Restrictive Account Lockout Mechanism Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run KNX Association KNX Protocol Connection Authorization Option 1. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-07-15, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-07-29 ; treat that as the outer limit, not the target.
- EPSS 1.3% , percentile 70: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 70% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Check exposure. KNX CVE-2023-4346: Building Automation BCU Key Lockout — Only buildings with KNX devices that have no BCU key set and a network path to the KNX bus are at risk, but there is no patch and a lockout can mean physically replacing devices.

## What it is

KNX devices that use KNX Connection Authorization and support Option 1 are, depending on the implementation, vulnerable to being locked and users being unable to reset them to gain access to the device. The BCU key feature on the devices can be used to create a password for the device, but this password can often not be reset without entering the current password. If the device is configured to interface with a network, an attacker with access to that network could interface with the KNX installation, purge all devices without additional security options enabled, and set a BCU key, locking the device. Even if a device is not connected to a network, an attacker with physical access to the device could also exploit this vulnerability in the same way.

## Affected products (CVE record)

- KNX Association KNX Protocol Connection Authorization Option 1: 0

## Severity

- icscert CVSS 3.1: 7.5 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

## Exploitation

- CISA KEV: added 2026-07-15; federal due date 2026-07-29. Known ransomware use: Unknown.
- CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 1.29% probability of exploitation activity in the next 30 days; percentile 70.

## Sources

- [CVE.org record CVE-2023-4346](https://www.cve.org/CVERecord?id=CVE-2023-4346)
- [NVD entry CVE-2023-4346](https://nvd.nist.gov/vuln/detail/CVE-2023-4346)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-4346)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/ics-advisories/icsa-23-236-01)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)

---
Source page: https://erroneo.us/security/cve/CVE-2023-4346/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt