Grav vulnerable to Server Side Template Injection (SSTI) via Twig escape handler

Vulnerability Description

Grav is an open-source, flat-file content management system. Prior to version 1.7.45, due to the unrestricted access to twig extension class from grav context, an attacker can redefine the escape function and execute arbitrary commands. Twig processing of static pages can be enabled in the front matter by any administrative user allowed to create or edit pages. As the Twig processor runs unsandboxed, this behavior can be used to gain arbitrary code execution and elevate privileges on the instance. Version 1.7.45 contains a patch for this issue.

References

• https://github.com/getgrav/grav/security/advisories/GHSA-2m7x-c7px-hp58
• https://github.com/getgrav/grav/commit/de1ccfa12dbcbf526104d68c1a6bc202a98698fe
• https://github.com/twigphp/Twig/blob/3.x/src/Extension/EscaperExtension.php#L99