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CVE-2023-4346.

Severity, exploit probability and exploitation status for one vulnerability, drawn from NVD, FIRST EPSS and CISA's exploited catalogue.

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known exploited KNX Association KNX Protocol Connection Authorization Option 1 Overly Restrictive Account Lockout Mechanism Vulnerability

Vendor / product
KNX Association - KNX Protocol Connection Authorization Option 1
Listed by CISA
2026-07-15
Federal fix deadline
2026-07-29 (passed)
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.

Scores

CVSS 3.1
7.5 high CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
0.91% estimated probability of exploitation in the next 30 days (higher than 56% of all CVEs)
Weakness class
CWE-645

ATT&CK techniques

inferred from weakness class no curated mapping exists for this CVE; these are the techniques typically seen with CWE-645 vulnerabilities

ReconnaissanceResource DevelopmentInitial AccessExecutionPersistencePrivilege EscalationStealthDefense ImpairmentCredential AccessDiscoveryLateral MovementCollectionCommand and ControlExfiltrationImpact

T1531 Account Access Removal

Impact

Adversaries may interrupt availability of system and network resources by inhibiting access to accounts utilized by legitimate users.

Inferred from CWE-645.

See these techniques on the full ATT&CK matrix.

Description

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.

Published
2023-08-29
Last modified
2026-07-16
NVD status
Analyzed

References

CVSS measures how bad exploitation would be; EPSS estimates how likely exploitation is within 30 days; the CISA listing means it is already happening. Read them together: a CVSS 9.8 with EPSS 0.04% is usually less urgent than a CVSS 7.2 on the exploited list. Data: NVD, FIRST EPSS, CISA KEV; detail is cached for a week, scores for a day. ATT&CK techniques come from the CTID KEV mappings project where a curated mapping exists, otherwise they are inferred from the weakness class and labelled as such. ATT&CK is a registered trademark of The MITRE Corporation. © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation.