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ABB Cylon FLXeon 9.3.5 (bbmdList.js) Authenticated Config Poisoning

Critical
Advisory ID
ZSL-2025-5935
Release Date
19 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 suffers from a configuration poisoning vulnerability in the put() function of bbmdList.js, where the writeFile() function is invoked to persist user-controlled data (req.body.bipList and req.body.natList) directly into sensitive configuration files (/etc/bdt.txt and /etc/bdt2.txt). This write operation lacks input validation and integrity checks allowing an attacker to supply crafted JSON payloads to inject or overwrite trusted BACnet BBMD entries. As these files are critical for network configuration, exploitation may result in unauthorized network redirection, denial of service, or insertion of rogue nodes into the system, thereby undermining the integrity and security of OT network communications.

Proof of Concept
Disclosure Timeline
21.04.2024Vulnerability discovered.
22.04.2024Vendor contacted.
22.04.2024Vendor responds.
02.05.2024Working with the vendor.
18.05.2025No response from the vendor.
19.05.2025Public security advisory released.
Credits
Vulnerability discovered by Gjoko Krstic
References
Changelog
19.05.2025Initial release