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cnvd-2025-30339

EUVD-2026-262247

fkie_cve-2025-66299

Grav is a file-based Web platform. Prior to 1.8.0-beta.27, Grav CMS is vulnerable to a Server-Side Template Injection (SSTI) that allows any authenticated user with editor permissions to execute arbitrary code on the remote server, bypassing the existing security sandbox. Since the security sandbox does not fully protect the Twig object, it is possible to interact with it (e.g., call methods, read/write attributes) through maliciously crafted Twig template directives injected into a web page. This allows an authenticated editor to add arbitrary functions to the Twig attribute system.twig.safe_filters, effectively bypassing the Grav CMS sandbox. This vulnerability is fixed in 1.8.0-beta.27.

GHSA-gjc5-8cfh-653x — Grav is Vulnerable to Security Sandbox Bypass with SSTI (Server Side Template Injection)

Affected: Packagist: getgrav/grav

## Summary

Grav CMS is vulnerable to a Server-Side Template Injection (SSTI) that allows any authenticated user with editor permissions to execute arbitrary code on the remote server, bypassing the existing security sandbox.

## Details

Grav CMS uses a custom sandbox to protect the powerful Twig methods such as `registerUndefinedFilterCallback()`. These methods are designed to prevent SSTI attacks by denying the execution of dangerous PHP functions (e.g., `exec()`, `passthru()`, `system()`, etc.) within Twig template directives.

The current defense mechanism relies on a blacklist of prohibited functions (PHP, Twig), checked through the `isDangerousFunction()` method in the file `system/src/Grav/Common/Twig.php`:

```php $this->twig->registerUndefinedFilterCallback(function (string $name) use ($config) { $allowed = $config->get('system.twig.safe_filters'); if (is_array($allowed) && in_array($name, $allowed, true) && function_exists($name)) { return new TwigFilter($name, $name); } if ($config->get('system.twig.undefined_filters')) { if (function_exists($name)) { if (!Utils::isDangerousFunction($name)) { user_error("PHP function {$name}() used as Twig filter. This is deprecated in Grav 1.7. Please add it to system configuration: `system.twig.safe_filters`", E_USER_DEPRECATED);

return new TwigFilter($name, $name); }

/** @var Debugger $debugger */ $debugger = $this…