CVE-2023-34252 Information

Description

Grav is a file-based Web platform. Prior to version 1.7.42 there is a logic flaw in the GravExtension.filterFilter() function whereby validation against a denylist of unsafe functions is only performed when the argument passed to filter is a string. However passing an array as a callable argument allows the validation check to be skipped. Consequently a low privileged attacker with login access to Grav Admin panel and page creation/update permissions is able to inject malicious templates to obtain remote code execution. The vulnerability can be found in the GravExtension.filterFilter() function declared in /system/src/Grav/Common/Twig/Extension/GravExtension.php. Version 1.7.42 contains a patch for this issue. End users should also ensure that twig.undefined_functions and twig.undefined_filters properties in /path/to/webroot/system/config/system.yaml configuration file are set to false to disallow Twig from treating undefined filters/functions as PHP functions and executing them.

Reference

https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Twig/Extension/GravExtension.php#L1692-L1698 https://github.com/getgrav/grav/security/advisories/GHSA-96xv-rmwj-6p9w https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Utils.php#L1956-L2074 https://github.com/getgrav/grav/commit/244758d4383034fe4cd292d41e477177870b65ec