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CVE-2023-4346

KNX devices that use KNX Connection Authorization and support Option 1 are, depending on the implementation, vulnerable to being locked and users being unable…

High Known exploited
Severity
7.5 / 10
High · CVSS 3.1
Exploit chance (EPSS)
1.36%
Chance of exploitation in the next 30 days. Higher than 71.79% of scored vulnerabilities.
Known exploited
Yes
In CISA's catalog since Jul 15, 2026
Weakness
CWE-645 Overly Restrictive Account Lockout Mechanism
Fix
None yet
No fixed version published
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). 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. Due for U.S. federal agencies by Jul 29, 2026.

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.

How to fix

No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.

Severity breakdown

CVSS 3.1 7.5

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

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Weakness

CWE-645: Overly Restrictive Account Lockout Mechanism

The product contains an account lockout protection mechanism, but the mechanism is too restrictive and can be triggered too easily, which allows attackers to deny service to legitimate users by causing their accounts to be locked out.

How to prevent it
  • Architecture and Design: Implement more intelligent password throttling mechanisms such as those which take IP address into account, in addition to the login name.
  • Architecture and Design: Implement a lockout timeout that grows as the number of incorrect login attempts goes up, eventually resulting in a complete lockout.
  • Architecture and Design: Consider alternatives to account lockout that would still be effective against password brute force attacks, such as presenting the user machine with a puzzle to solve (makes it do some computation).

References

Advisories

Other links

Timeline

  1. Published
  2. Added to CISA's Known Exploited Vulnerabilities catalog
  3. Last updated by the source
  4. Remediation due for U.S. federal agencies
  5. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-v5gf-vpjc-pc7w
Payload: Unauthenticated account-lockout denial of service
High Same weakness, CWE-645
GO-2025-3692
Mattermost Fails to Lockout LDAP Users After Repeated Login Failures
Medium Same weakness, CWE-645
GHSA-cq42-vhv7-xr7p
Keycloak Denial of Service via account lockout
Medium Same weakness, CWE-645
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