CVE-2023-34252
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.07%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.2 HIGHCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 2.07% probability · 80th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-184, CWE-1336, CWE-94
- Affected
- getgrav/grav
- Source
- security-advisories@github.com
References
- https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Twig/Extension/GravExtension.php#L1692-L1698Issue Tracking
- https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Utils.php#L1956-L2074Issue Tracking
- https://github.com/getgrav/grav/commit/244758d4383034fe4cd292d41e477177870b65ecPatch
- https://github.com/getgrav/grav/security/advisories/GHSA-96xv-rmwj-6p9wExploit, Vendor Advisory
- https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Twig/Extension/GravExtension.php#L1692-L1698Issue Tracking
- https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Utils.php#L1956-L2074Issue Tracking
- https://github.com/getgrav/grav/commit/244758d4383034fe4cd292d41e477177870b65ecPatch
- https://github.com/getgrav/grav/security/advisories/GHSA-96xv-rmwj-6p9wExploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.