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ABB Cylon FLXeon 9.3.4 Limited Cross-Site Request Forgery (RCE)

Medium
Advisory ID
ZSL-2025-5918
Release Date
11 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

A CSRF vulnerability has been identified in the ABB Cylon FLXeon series. However, exploitation is limited to specific conditions due to the server's CORS configuration (Access-Control-Allow-Origin: * without Access-Control-Allow-Credentials: true). The vulnerability can only be exploited under the following scenarios: Same Domain: The attacker must host the malicious page on the same domain as the target server. Man-in-the-Middle (MitM): The attacker can intercept and modify traffic between the user and the server (e.g., on an unsecured network). Local Area Network (LAN) Access: The attacker must have access to the same network as the target server. Subdomains: The attacker can host the malicious page on a subdomain if the server allows it. Misconfigured CORS: The server’s CORS policy is misconfigured to allow certain origins or headers. Reflected XSS: The attacker can exploit a reflected XSS vulnerability to execute JavaScript in the context of the target origin.

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.
11.02.2025Public security advisory released.
Credits
Vulnerability discovered by Gjoko Krstic
References
Changelog
11.02.2025Initial release
12.02.2025Added reference [2]
09.05.2025Added reference [3]