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ABB Cylon FLXeon 9.3.4 (serialConfig.js) JSON Object Flooding DoS

High
Advisory ID
ZSL-2025-5915
Release Date
08 February 2025
Vendor
Affected Version
FLXeon Series (FBXi Series, FBTi Series, FBVi Series), CBX Series (FLX Series), CBT Series, CBV Series, Firmware: <=9.3.4
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 is vulnerable to an authenticated JSON flooding attack, leading to uncontrolled resource consumption and a denial-of-service (DoS) condition. The /api/serialConfig endpoint allows an authenticated attacker to abuse an unrestricted loop to create a large number of JSON objects by sending specially crafted requests through the ports JSON array. This results in excessive memory and CPU usage, causing resource exhaustion and potential service failure.

Proof of Concept
Disclosure Timeline
21.04.2024Vulnerability discovered.
22.04.2024Vendor contacted.
22.04.2024Vendor responds.
02.05.2024Working with the vendor.
20.01.2025Vendor releases version 9.3.5 to address this issue.
08.02.2025Public security advisory released.
Credits
Vulnerability discovered by Gjoko Krstic
References
Changelog
08.02.2025Initial release
10.02.2025Added reference [1]
26.05.2025Added reference [2]