High CVSS 7.5 Actively exploited · CISA KEV

KNX Association KNX Protocol Connection Authorization Option 1

CVE-2023-4346 Added Jul 15, 2026 Remediation due in 12 days

TL;DR

KNX Association KNX Protocol Connection Authorization Option 1 is affected by a high-severity vulnerability (CVE-2023-4346) that is confirmed to be actively exploited in the wild. 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.

What is this vulnerability?

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.

How it works

This is classified as CWE-645. In plain terms, an attacker could use this flaw in KNX Protocol Connection Authorization Option 1 to gain access, disrupt service, or steal data — the exact impact depends on how it’s deployed in your environment.

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Mitigations

Apply the vendor’s security patch or update as soon as it’s available and tested.
If no patch exists yet, apply the vendor’s temporary workaround.
Limit network exposure of the affected system until it’s patched.
Review logs for signs of prior exploitation, especially if it’s flagged for ransomware use.

Recommendations

Confirm whether KNX Association KNX Protocol Connection Authorization Option 1 is used anywhere in your environment.
Patch internet-facing systems first, then internal ones.
Set a reminder ahead of the remediation deadline so it doesn’t slip.
Subscribe to the vendor’s security advisories for earlier warning next time.

Compiled from public threat intelligence (CISA Known Exploited Vulnerabilities catalog and the National Vulnerability Database, referenced in 3 public advisories).