ABB Cylon FLXeon 9.3.5 (uukl.js) Predictable Salt and Weak Hashing Algorithm


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: <=9.3.5

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 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.

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-2025-5936
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2025-5936.php


21.04.2024

--


$ cat project

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$ sed -n '10,39p' api/uukl.js | awk '{print NR+2, $0}'

10: function verify(passwd, defpwd = false) {
11:     var pwdFileName;
12:     if (!defpwd)
13:         pwdFileName = pwdFile;
14:     else
15:         pwdFileName = defPwdFile;
16:     const data = fs.readFileSync(pwdFileName, 'utf-8');
17:     const split = data.toString().split(' ');
18:     const salt = split[0];
19:     const savedHash = split[1].trim();
20:     const md5sum = crypto.createHash('md5');
21:     md5sum.update(salt);
22:     md5sum.update(passwd);
23:     const hash = md5sum.digest('hex');
24:     if (hash == savedHash) {
25:         return true;
26:     }
27:     else {
28:         Jrpc.doJrpc('cbxi', { method: 'uuklPwd', params: { action: 'fail' } }, (reply) => { });
29:         return false;
30:     }
31: }
32: function change(passwd) {
33:     var md5sum = crypto.createHash('md5');
34:     var salt = Math.floor(Math.random() * 100000).toString();
35:     md5sum.update(salt);
36:     md5sum.update(passwd);
37:     var hash = md5sum.digest('hex');
38:     fs.writeFileSync(pwdFile, salt + ' ' + hash);
39: }