high CVSS 8.8

CVE-2026-40488·PHP vulnerability

Magento Long Term Support (LTS) is an unofficial, community-driven project provides an alternative to the Magento Community Edition e-commerce platform with a high level of backward compatibility. Prior to version 20.17.0, the product custom option file upload in OpenMage LTS uses an incomplete blocklist (`forbidden_extensions = php,exe`) to prevent dangerous file uploads. This blocklist can be trivially bypassed by using alternative PHP-executable extensions such as `.phtml`, `.phar`, `.php3`, `.php4`, `.php5`, `.php7`, and `.pht`. Files are stored in the publicly accessible `media/custom_options/quote/` directory, which lacks server-side execution restrictions for some configurations, enabling Remote Code Execution if this directory is not explicitly denied script execution. Version 20.17.0 patches the issue.

Severity
high
Software
PHP
Fixed in
20.17.0
Published
2026-04-20

Affected versions

Until: 20.17.0

Fixed in: 20.17.0

How to fix this CVE

Upgrade OpenMage LTS to version 20.17.0 or later, which implements a comprehensive file extension blocklist and enforces server-side execution restrictions on the media/custom_options/quote/ directory. If immediate patching is not possible, manually configure your web server to deny script execution in the custom options upload directory and implement a strict file type validation policy beyond the default blocklist. Review your web server configuration to ensure .phtml, .phar, .php3, .php4, .php5, .php7, and .pht files cannot be executed in upload directories.

sudo dnf check-update php && sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /media/custom_options/quote/ with multipart form data containing files with extensions matching \.(phtml|phar|php[3-7]|pht)$ followed by HTTP requests to the uploaded file path attempting code execution

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block all POST requests to /media/custom_options/quote/ that contain file uploads with extensions: .phtml, .phar, .php3, .php4, .php5, .php7, .pht. Additionally, configure your WAF to return 403 Forbidden for any requests attempting to execute scripts in the media/custom_options/ directory.

How to check if you are affected

  1. Check OpenMage LTS version: grep -r 'VERSION' /path/to/openmage/app/Mage.php | head -1
  2. Verify media directory permissions: ls -la /path/to/openmage/media/custom_options/quote/ and check if script execution is disabled in .htaccess or web server config
  3. Search web server error and access logs for suspicious file uploads: grep -E '\.phtml|\.phar|\.php[3-7]|\.pht' /var/log/apache2/access.log* or /var/log/nginx/access.log*
  4. Verify the fix by confirming version 20.17.0 is installed: grep -r 'VERSION' /path/to/openmage/app/Mage.php and test file upload restrictions by attempting to upload a .phtml file

Indicators of compromise

  • File upload attempts to /media/custom_options/quote/ with .phtml, .phar, or .php* variant extensions
  • Access attempts to media/custom_options/quote/*.phtml or similar executable variants
  • POST requests with Content-Disposition filenames ending in php3, php4, php5, php7, phar, or pht

FAQ

What is CVE-2026-40488?

This vulnerability exists in OpenMage LTS's custom option file upload feature, which uses an insufficient blocklist that only prevents .php and .exe files. Attackers can bypass this by uploading files with alternative PHP-executable extensions, leading to remote code execution if the upload directory permits script execution.

Is CVE-2026-40488 being actively exploited?

No, according to CISA KEV data, CVE-2026-40488 is not currently being actively exploited in the wild, though the attack is trivial and publicly documented.

What versions of OpenMage LTS are affected by CVE-2026-40488?

All versions prior to 20.17.0 are affected by this vulnerability. Version 20.17.0 and later include the security patch.

How do I check if my server is vulnerable to CVE-2026-40488?

Run: php -v to confirm PHP version, then check your OpenMage installation version in app/Mage.php. Verify if your media/custom_options/quote/ directory has execution restrictions in .htaccess or your web server configuration.

Does Defensia detect CVE-2026-40488?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If PHP and OpenMage LTS are installed on a monitored server, CVE-2026-40488 will appear in your dashboard with remediation steps.

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References

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