Actively exploited in the wild
KNX Association KNX Protocol Connection Authorization Option 1 Overly Restrictive Account Lockout Mechanism Vulnerability
KNX Association - KNX Protocol Connection Authorization Option 1 · Listed in the CISA KEV since 2026-07-15. This indicates confirmed attacks in production environments.
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.
CVE-2023-4346
HighCVSS 7.5KEVExploitation Probability (EPSS)
Elevated risk54th percentile - higher than 54% of all known CVEs
Summary
KNX devices using KNX Connection Authorization and supporting Option 1 can be locked, preventing users from resetting them to regain access. An attacker with network or physical access can set a BCU key, locking the device.
Risk Assessment
The risk is permanent loss of access to KNX devices, potentially disrupting building automation systems and requiring costly hardware replacement.
Recommendation
Update KNX device firmware to a version that fixes this vulnerability and enable additional security options to prevent unauthorized BCU key setting.
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Original NVD description (English source)
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.