ExpressionEngine <= 6.0.2 (Translate::save) PHP Code Injection Vulnerability

• Software Link:

https://expressionengine.com/

• Affected Versions:

Version 6.0.2 and prior versions.
Version 5.4.1 and prior versions.

• Vulnerability Description:

The vulnerable code is located in the “ExpressionEngine\Controller\Utilities\Translate::save()” method:

    private function save($language, $file)
    {
        
        $file = ee()->security->sanitize_filename($file);

        $dest_dir = $this->languages_dir . $language . '/';
        $filename = $file . '_lang.php';
        $dest_loc = $dest_dir . $filename;

        $str = '<?php' . "\n" . '$lang = array(' . "\n\n\n";

        ee()->lang->loadfile($file);

        foreach ($_POST as $key => $val) {
            $val = str_replace('<script', '', $val);
            $val = str_replace('<iframe', '', $val);
            $val = str_replace(array("\\", "'"), array("\\\\", "\'"), $val);

            $str .= '\'' . $key . '\' => ' . "\n" . '\'' . $val . '\'' . ",\n\n";
        }

        $str .= "''=>''\n);\n\n";
        $str .= "// End of File";

        $this->load->helper('file');

        if (write_file($dest_loc, $str)) {
            ee('CP/Alert')->makeInline('shared-form')
                ->asSuccess()
                ->withTitle(lang('translations_saved'))
                ->addToBody(sprintf(lang('file_saved'), $dest_loc))
                ->defer();

User input passed via keys of POST parameters is not properly sanitized before being assigned to the “$str” variable at line 380. Such a variable will be used in a call to the “write_file()” function at line 402, trying to write user supplied content into the /system/user/language/[lang]/[file]_lang.php file. This can be exploited to inject and execute arbitrary PHP code. Successful exploitation of this vulnerability requires an account with permissions to access the CP translation system utilities.

• Solution:

Upgrade to version 6.0.3, 5.4.2, or later.

• Disclosure Timeline:

[03/02/2021] – Vendor notified through HackerOne
[15/02/2021] – Vulnerability acknowledged by the vendor
[16/02/2021] – CVE number assigned
[17/02/2021] – Version 6.0.3 released
[04/03/2021] – Version 5.4.2 released
[15/03/2021] – Public disclosure

• CVE Reference:

The Common Vulnerabilities and Exposures project (cve.mitre.org)
has assigned the name CVE-2021-27230 to this vulnerability.

• Credits:

Vulnerability discovered by Egidio Romano.

• Other References:

https://hackerone.com/reports/1093444