Headline
ABB Cylon FLXeon 9.3.5 (uukl.js) Predictable Salt and Weak Hashing Algorithm
The ABB Cylon FLXeon BACnet controller’s /api/uukl.js module implements password verification and update mechanisms using the insecure MD5 hash function alongside weak salt generation via Math.random(). This constitutes a cryptographic vulnerability where password hashes are susceptible to collision and brute-force attacks due to MD5’s known weaknesses and the low entropy of the salt. Specifically, in the verify() and change() functions, passwords are hashed using MD5 with predictable, non-cryptographically secure salts, then stored in plaintext-accessible files. This undermines the integrity of the authentication process, enabling attackers with file system access or knowledge of the implementation to precompute hash values or mount dictionary attacks.
Title: ABB Cylon FLXeon 9.3.5 (uukl.js) Predictable Salt and Weak Hashing Algorithm
Advisory ID: ZSL-2025-5936
Type: Local/Remote
Impact: Security Bypass
Risk: (3/5)
Release Date: 19.05.2025
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/uukl.js module implements password verification and update mechanisms using the insecure MD5 hash function alongside weak salt generation via Math.random(). This constitutes a cryptographic vulnerability where password hashes are susceptible to collision and brute-force attacks due to MD5’s known weaknesses and the low entropy of the salt. Specifically, in the verify() and change() functions, passwords are hashed using MD5 with predictable, non-cryptographically secure salts, then stored in plaintext-accessible files. This undermines the integrity of the authentication process, enabling attackers with file system access or knowledge of the implementation to precompute hash values or mount dictionary attacks.
Vendor
ABB Ltd. - https://www.global.abb
Affected Version
FLXeon Series (FBXi Series, FBTi Series, FBVi Series)
CBX Series (FLX Series)
CBT Series
CBV Series
Firmware: <=9.3.5
Tested On
Linux Kernel 5.4.27
Linux Kernel 4.15.13
NodeJS/8.4.0
Express
Vendor Status
[21.04.2024] Vulnerability discovered.
[22.04.2024] Vendor contacted.
[22.04.2024] Vendor responds.
[02.05.2024] Working with the vendor.
[18.05.2025] No response from the vendor.
[19.05.2025] Public security advisory released.
PoC
abb_flxeon_crypto1.txt
Credits
Vulnerability discovered by Gjoko Krstic - <[email protected]>
References
N/A
Changelog
[19.05.2025] - Initial release
Contact
Zero Science Lab
Web: https://www.zeroscience.mk
e-mail: [email protected]