CVE-2015-7339 Bypass File Upload Restriction in JCE Joomla Component

1. Vulnerability Properties

Title: Bypass File Upload Restriction in JCE Joomla Component
CVE ID: CVE-2015-7339
CVSSv3 Base Score: 7.4 (AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L)
Vendor: Joomla Content Editor
Products: JCE
Advisory Release Date: 15 October 2015
Advisory URL: https://labs.integrity.pt/advisories/cve-2015-7339
Credits: Discovery by Fábio Pires <fp[at]integrity.pt>, Filipe Reis <fr[at]integrity.pt>, Vitor Oliveira <vo[at]integrity.pt>

2. Vulnerability Summary

This issue allows a malicious user to bypass the file upload validation, from version 2.5.0 to 2.5.2.

3. Technical Details

By using the JCE's File Browser available on

Administration >  Components > JCE Editor > Control Panel > File Browser

you will be able to bypass the upload validation system in order to upload a malicious image file with some php code in the exif headers (comments field).

In the source code of /com_jce/editor/libraries/classes/browser.php you can find the following validations:

This code will check every uploaded file and look if the string <?php is inside it, but it will only check the short open tag version in the files specified on preg_match function.

So, if you upload an image with a short open tag code, and save it as a php file, you will be able to bypass this validation system.

In order to explain the process, here are some images:

1 - Create an image file using short open tags and some php code in the comment field.

2 - Upload the image file and change the name field to a php file extension. (bypass javascript validation)

3 - The server will respond with a 200 OK, letting you know that the file was sucessfully uploaded.

4 - Uploaded file will be in the folder you specified on upload-dir field.

5 - File can be executed and remote code execution can be done.

This issue can become more critical if you allow users to use JCE plugin as a primary plugin for comments.

This vulnerability has been patched in the JCE version 2.5.3.

4. Vulnerable Versions

• From 2.5.0 to 2.5.2

5. Solution

• Update to 2.5.3 or latest version available

6. Vulnerability Timeline

• September 01, 2015 — Bug reported to JCE
• September 01, 2015 — JCE’s team reply with patched version to test
• September 02, 2015 — JCE’s team releases a new version
• October 15, 2015 — Public disclosure

7. References

• https://www.joomlacontenteditor.net/news/item/jce-253-released