ABB Cylon FLXeon 9.3.4 (runtimeSetup.sh) Hidden Backdoor Account


Vendor: ABB Ltd.
Product web page: https://www.global.abb                   
Affected version: FLXeon Series (FBXi Series, FBTi Series, FBVi Series)
                  CBX Series (FLX Series)
                  CBT Series
                  CBV Series
                  Firmware: <=9.3.4

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.

Desc: The application has a hidden administrative account 'cxpro' that has write
access permissions to the device.

Tested on: Linux Kernel 5.4.27
           Linux Kernel 4.15.13
           NodeJS/8.4.0
           Express


Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
                            @zeroscience


Advisory ID: ZSL-2025-5914
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2025-5914.php


21.04.2024

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$ cat project

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$ cat /usr/local/aam/bin/runtimeSetup.sh | grep useradd
                useradd -u 950 -d /usr/local/aam/node-server/platform-dist -r -s /bin/sh -g admin -p '$6$jwix7x1XIB/$OS5/8TFhxckN5sc2KZCe3xfmX3VX8E3UPf7GE3vKhWJe8m6kY.7194fkH/o7wQLHYktzmTGay.BZnJqJUnHIX1' cxpro