Zen Cart 1.5.4: Code Execution and Information Leak

Date: 2015-09-14 10:58:01

Update: After the publication of this advisory, the vendor has released a new version 1.6.0 fixing these issues.

1. Introduction

2. Vulnerability Description: Arbitrary File Upload

When uploading an image for a record, there is no check as to what type or extension the file has, with the exception that it cannot be a htaccess file. These files are stored in the /image directory, which is protected from code execution via a htaccess file if the server is not prevented from parsing htaccess files correctly (which may for example be the case for speed and security reasons).

An attacker can perform a directory traversal via the img_dir POST parameter to store an uploaded image outside of this protected directory, thus gaining code execution or overwriting sensitive files, even if the image directory is protected by the htaccess file.

The recommendations for denying code execution listed in the help-page "Important Site Security Recommendations" - such as protecting the /image and /html_includes folders against file modification and execution - do not protect against code execution via this attack.

This problem exists for other classes performing file operations as well, such as media_manager.php, manufacturers.php, attributes_controller.php, mail.php, new_product_preview.php, record_company.php, product_types.php, and categories.php.

Please note that an admin account is required that has the right to edit one of the items that provide an image upload, such as the right "Catalog: Product Types" or "Extra: Record Artists"

3. Proof of Concept: Arbitrary File Upload

4. Further

Code Execution

With an admin account with the right "Tools: Define Pages Editor" it is possible to edit a limited number of PHP files which mainly contain HTML here: http://localhost/zen-cart-v1.5.4-12302014/admin2/define_pages_editor.php?define_it=4&action=new_page.

Execution of these files is prohibited via htaccess files, so with correct server configuration, the intention seems to be that an attacker should not be able to gain code execution via this editor.

However, the protection against code execution is insufficient, as any injected code will be executed once the file is included. For example:

1. visit http://localhost/zen-cart-v1.5.4-12302014/admin2/define_pages_editor.php?define_it=8&action=new_page
2. add <?php passthru($_GET['e']); ?>
3. visit http://localhost/zen-cart-v1.5.4-12302014/index.php?main_page=nonexistent&cPath=2&e=ls%20-alF

Please note that if the user followed the guide "Important Site Security Recommendations", they will have set these files to read-only, disallowing code execution.

Information Leak

Via a directory traversal on the products_image_large_additional parameter, an attacker can check if a file exists on the server, thus gaining information about installed software. Viewing of the file is not possible.

Example:

5. Solution

To mitigate the information leak a patch can be used: https://www.zen-cart.com/showthread.php?218239-curesec-security-report-Patch-Included

The Arbitrary File Upload vulnerability has not been fixed yet.

Update: The vendor has fixed the file upload vulnerability in version 1.6.0.

6. Report Timeline