← Advisories

ABB Cylon FLXeon 9.3.5 (variant.js) Unauthenticated System Information Disclosure

High
Advisory ID
ZSL-2025-5937
Release Date
21 May 2025
Vendor
Affected Version
FLXeon Series (FBXi Series, FBTi Series, FBVi Series), CBX Series (FLX Series), CBT Series, CBV Series, Firmware: <=9.3.5
CVE
N/A
Tested On
Linux Kernel 5.4.27, Linux Kernel 4.15.13, NodeJS/8.4.0, Express
Summary

BACnet® Smart Building Controllers. ABB's BACnet portfolio features a series of BACnet® IP and BACnet MS/TP field controllers for ASPECT® and INTEGRA™ building management solutions. ABB BACnet controllers are designed for intelligent control of HVAC equipment such as central plant, boilers, chillers, cooling towers, heat pump systems, air handling units (constant volume, variable air volume, and multi-zone), rooftop units, electrical systems such as lighting control, variable frequency drives and metering.

The FLXeon Controller Series uses BACnet/IP standards to deliver unprecedented connectivity and open integration for your building automation systems. It's scalable, and modular, allowing you to control a diverse range of HVAC functions.

Description

The ABB Cylon FLXeon BACnet controller's /api/variant endpoint exposes sensitive system information, including the internal IP address, MAC address, device model, and build type, without requiring authentication. The get() function gathers network interface data using the os.networkInterfaces() API and returns it in the HTTP response, potentially allowing unauthenticated clients to fingerprint internal infrastructure and gain insight into the device's network configuration and hardware characteristics.

Proof of Concept
Disclosure Timeline
21.04.2024Vulnerability discovered.
22.04.2024Vendor contacted.
22.04.2024Vendor responds.
02.05.2024Working with the vendor.
20.05.2025No response from the vendor.
21.05.2025Public security advisory released.
Credits
Vulnerability discovered by Gjoko Krstic
References
Changelog
21.05.2025Initial release