CVE-2023-34252

Description

Grav is a flat-file content management system. 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.

Weakness classification

• security-advisories@github.com: CWE-184
• nvd@nist.gov: CWE-94

Primary references

• security-advisories@github.com — Issue Tracking
• security-advisories@github.com — Issue Tracking
• security-advisories@github.com — Patch
• security-advisories@github.com — Exploit, Vendor Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Issue Tracking
• af854a3a-2127-422b-91ae-364da2661108 — Issue Tracking
• af854a3a-2127-422b-91ae-364da2661108 — Patch
• af854a3a-2127-422b-91ae-364da2661108 — Exploit, Vendor Advisory