Vendor description
"flatCore is based on PHP and PDO/SQLite. The Core is as minimalistic as possible, but can be easily extended by the modular structure. If you are looking for a solution to edit your website live and with ease, flatCore may be your buddy."
Source: https://flatcore.org/
Business recommendation
The vendor provides an updated version which should be installed immediately. An in-depth security analysis performed by security professionals is highly advised, as the software may be affected from further security issues.
Vulnerability Overview / Description
1) Reflected Cross-Site Scripting (Authenticated user) (CVE-2021-23838)
A reflected cross-site scripting vulnerability was identified in the 'media_filter' HTTP request body parameter for the 'acp' interface. The affected parameter accepts malicious client side script without proper input sanitization. For example, a malicious user can leverage this vulnerability to steal cookies from a victim user and perform a session hijacking attack which may then lead to unauthorized access to the site.
2) Stored Cross-Site Scripting (Authenticated user) (CVE-2021-23836)
A stored cross-site scripting vulnerability was identified in the 'prefs_smtp_psw' HTTP request body parameter for the 'acp' interface. An admin user can inject malicious client side script to the affected parameter without any form of input sanitization. The injected payload will be executed in the browser of a user whenever one visits the affected module page.
3) Local File Disclosure (Authenticated user) (CVE-2021-23835)
A local file disclosure vulnerability was identified in the 'docs_file' HTTP request body parameter for the 'acp' interface which can be exploited with admin access rights. The affected parameter which retrieves the contents of the specified file was found to be accepting malicious user inputs without proper input sanitization, thus leading to retrieval of backend server sensitive files, for example /etc/passwd, sqlite database files, PHP source code etc.
4) Time Based Blind SQL Injection (Authenticated user) (CVE-2021-23837)
A time based blind SQL injection was identified in the 'selected_folder' HTTP request body parameter for the 'acp' interface. The affected parameter which retrieves the file contents of the specified folder was found to be accepting malicious user inputs without proper input sanitization, thus leading to SQL injection. Database related information can be successfully retrieved.
Proof Of Concept
1) Reflected Cross-Site Scripting (Authenticated user) (CVE-2021-23838)
An authenticated admin user can exploit this vulnerability by manipulating the 'media_filter' parameter found in the Files/ Manage Files module.
URL : http:// $HOST/acp/acp.php?tn=filebrowser&sub=browse METHOD : POST PARAMETER : media_filter PAYLOAD : aaa%3cscript%3ealert(document.cookie)%3c%2fscript%3ebbb
2) Stored Cross-Site Scripting (Authenticated user) (CVE-2021-23836)
An authenticated admin user can exploit this vulnerability by manipulating the 'prefs_smtp_psw' parameter found in the System/ E-Mail module.
URL : http:// $HOST/acp/acp.php?tn=system&sub=mail METHOD : POST PARAMETER : prefs_smtp_psw PAYLOAD : '%3e%3cscript%3ealert(document.cookie)%3c%2fscript%3eaaabbb
3) Local File Disclosure (Authenticated user) (CVE-2021-23835)
An authenticated admin user can exploit this vulnerability by manipulating the 'docs_file' parameter found in the help module.
URL : http:// $HOST/acp/acp.php METHOD : POST PARAMETER : docs_file PAYLOAD : %2E%2E%2F%2E%2E%2F%2E%2E%2F%2E%2E%2F%2E%2E%2Fetc%2Fpasswd
4) Time Based Blind SQL Injection (Authenticated user) (CVE-2021-23837)
An authenticated admin user can exploit this vulnerability by manipulating the 'selected_folder' parameter found in the Files/ Manage Files module.
URL : http:// $HOST/acp/acp.php?tn=filebrowser&sub=browse
METHOD : POST
PARAMETER : selected_folder
PAYLOAD : %' AND 8483=LIKE('ABCDEFG',UPPER(HEX(RANDOMBLOB(500000000/2)))) AND 'eJQr%'='eJQr
Vulnerable / Tested Versions
flatCore CMS version 2.0.0 (Build 122) has been tested, which was the latest version available at the time of the test. Previous versions may also be affected.