ABB Busch-Welcome 2 Wire Door Opener Actuator

Summary

ABB disclosed CVE-2025-7705, an authentication bypass vulnerability in Busch-Welcome 2 Wire Door Opener Actuators (Switch Actuator 4 DU models) due to compatibility mode enabled by default. The flaw allows attackers to gain unauthorized physical access to buildings. ABB provides an on-site mitigation: toggling the mode switch and performing a power reset to recalibrate the system.

Full text

ICS Advisory ABB Busch-Welcome 2 Wire Door Opener Actuator Release DateMay 28, 2026 Alert CodeICSA-26-148-04 Related topics: Industrial Control System Vulnerabilities, Industrial Control Systems View CSAF Summary ABB is aware of vulnerabilities in the product versions listed as affected in the advisory. An attacker who successfully exploited this vulnerability could gain physical, unauthorized access to a Building where the product is installed The following versions of ABB Busch-Welcome 2 Wire Door Opener Actuator are affected: Switch Actuator 4 DU vers:all/* Switch actuator, door/light 4 DU vers:all/* CVSS Vendor Equipment Vulnerabilities v3 6.8 ABB ABB Busch-Welcome 2 Wire Door Opener Actuator Active Debug Code Background Critical Infrastructure Sectors: Commercial Facilities Countries/Areas Deployed: Worldwide Company Headquarters Location: Switzerland Vulnerabilities Expand All + CVE-2025-7705 Authentication bypass due to compatibility mode enabled by default View CVE Details Affected Products ABB Busch-Welcome 2 Wire Door Opener Actuator Vendor:ABB Product Version:Switch Actuator 4 DU -83330 - All Versions, Switch actuator, door/light 4 DU -83330-500 - All Versions Product Status:known_affected Remediations MitigationThe following actions need to be executed on premise where the respective Busch-Welcome® System is installed: • While the Busch-Welcome® System is in operation, toggle the mode switch on the product from “Door-Open” - to “Light” – Mode, wait one second and switch back to “Door-Open” - Mode. • Restart the Busch-Welcome® System with a Power reset (mains power off and on again). By executing the above steps, the system will recalibrate itself during boot up and will correct the misconfiguration automatically. ABB recommends that customers apply the above listed actions at the earliest convenience. Relevant CWE: CWE-489 Active Debug Code Metrics CVSS Version Base Score Base Severity Vector String 3.1 6.8 MEDIUM CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Acknowledgments ABB PSIRT reported this vulnerability to CISA. Notice The information in this document is subject to change without notice, and should not be construed as a commitment by ABB. ABB provides no warranty, express or implied, including warranties of merchantability and fitness for a particular purpose, for the information contained in this document, and assumes no responsibility for any errors that may appear in this document. In no event shall ABB or any of its suppliers be liable for direct, indirect, special, incidental or consequential damages of any nature or kind arising from the use of this document, or from the use of any hard-ware or software described in this document, even if ABB or its suppliers have been advised of the possibility of such damages. This document and parts hereof must not be reproduced or copied without written permission from ABB, and the contents hereof must not be imparted to a third party nor used for any unauthorized purpose. All rights to registrations and trademarks reside with their respective owners. Mitigating factors ABB recommends double check the system handbook of a Busch-Welcome® two wire system regarding security advises for the correct installation. Legal Notice and Terms of Use This product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy). Recommended Practices CISA recommends users take defensive measures to minimize the exploitation risk of these vulnerabilities. Minimize network exposure for all control system devices and/or systems, and ensure they are not accessible from the internet. Locate control system networks and remote devices behind firewalls and isolate them from business networks. When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most recent version available. Also recognize VPN is only as secure as its connected devices. CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures. CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies. CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets. Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies. Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents. Advisory Conversion Disclaimer This ICSA is a verbatim republication of ABB PSIRT 9AKK108471A4556 from a direct conversion of the vendor's Common Security Advisory Framework (CSAF) advisory. This is republished to CISA's website as a means of increasing visibility and is provided "as-is" for informational purposes only. CISA is not responsible for the editorial or technical accuracy of republished advisories and provides no warranties of any kind regarding any information contained within this advisory. Further, CISA does not endorse any commercial product or service. Please contact ABB PSIRT directly for any questions regarding this advisory. Revision History Initial Release Date: 2025-07-21 Date Revision Summary 2025-07-21 1 Initial version. 2026-05-28 2 Initial CISA Republication of ABB PSIRT 9AKK108471A4556 advisory Legal Notice and Terms of Use This product is provided subject to this Notification and this Privacy & Use policy. Vendor ABB Tags Sector: Commercial Facilities Sector Topics: Industrial Control System Vulnerabilities, Industrial Control Systems Please share your thoughts We recently updated our anonymous product survey; we welcome your feedback. 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Indicators of Compromise

• cve — CVE-2025-7705

Entities