FAUST iServer 9.0.018.018.4 Local File Inclusion Vulnerability

=======================================================================
               title: Local file inclusion vulnerability
             product: Land Software - FAUST iServer
  vulnerable version: 9.0.017.017.1-3 - 9.0.018.018.4
       fixed version: 9.0.019.019.7, Version 10
          CVE number: CVE-2021-34805
              impact: high
            homepage: https://www.land-software.de
               found: 2021-05-25
                  by: Mario Keck (Atos Germany)
                      SEC Consult Vulnerability Lab

                      An integrated part of SEC Consult, an Atos company
                      Europe | Asia | North America

                      https://www.sec-consult.com

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Vendor description:
-------------------
(German) "Der FAUST iServer bringt Ihre FAUST- , FAUST Entry- und LIDOS-Datenbanken
ins Intranet und Internet. Er bietet hohe Sicherheit und eine einfache
Installation."

Source: http://www.land-software.de/lfs.fau?prj=iweb&dn=faust+iserver


Business recommendation:
------------------------
The vendor provides a hotfix for the identified vulnerable versions. As the
most actual version v10 of FAUST iServer is not vulnerable, no immediate action in
the form of a patch is required. The webroot of the server should not be on the
same partition as the operating system's root partition.


Vulnerability overview/description:
-----------------------------------
1) Local File Inclusion (CVE-2021-34805)
When a URL is requested, the FAUST iServer checks for the corresponding ".fau"
file on the operating system. ".fau" files can be compared with compiled
webserver pages for displaying the content of the webpage. The identified
vulnerable versions of FAUST iServer do not properly protect against a request
aiming to read local files of the operating system.

FAUST iServer is designed to work on Windows operating systems only.
Therefore, by simply URL-encoding a path like
..\..\..\windows\win.ini into %2e%2e%5c%2e%2e%5c%2e%2e%5cwindows%5cwin.ini
the FAUST iServer returns the contents of win.ini


Proof of concept:
-----------------
1) Local File Inclusion (CVE-2021-34805)
The following proof of concept shows the HTTP request that was used to read
local files of the server's operating system.
The vulnerability, as shown in the proof of concept request below, can be
triggered as soon as a vulnerable version of FAUST iServer is in use. To read
operating system specific files, the webroot of FAUST iServer has to be located
on the same partition as the operating system root.
Authorization is not needed.

-------------------------------------------------------------------------------
HTTP Request:
GET /%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5cwindows%5cwin.ini HTTP/1.1
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
Connection: keep-alive
Host: <IP>
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Accept-Language: en-US,en;q=0.9
-------------------------------------------------------------------------------

Vulnerable / tested versions:
-----------------------------
The following versions have been tested and found to be vulnerable:
* 9.0.017.017.1-3
* 9.0.018.018.4


Vendor contact timeline:
------------------------
2021-06-10: Contacting vendor via email.
2021-06-14: Vendor requested more information about the vulnerability, which
             was provided on the same day.
2021-06-15: Requested information from vendor to check which versions are
             vulnerable.
2021-06-17: Vendor informed researcher about upcoming update and promised to
             inform all customers about the critical security fix in it.
2021-08-09: Confirmed the security fix in FAUST iServer 9.0.019.019.7.
2021-08-16: Researcher received a notification mail from the vendor's
             newsletter announcing the official release of the fixed version.
2022-01-12: Version 10 was officially released and is available for all
             customers for upgrade.
2022-01-20: Release of security advisory


Solution:
---------
The vulnerability is fixed in the following version:
* 9.0.019.019.7

This patch should be immediately installed.

Version 10 is not affected by this vulnerability, if possible it is recommended
to upgrade to this version.


Workaround:
-----------
None