high8.4Public exploit code

CVE-2021-29440

Grav's Twig processing allowing dangerous PHP functions by default

Public exploit code

Working exploit or proof of concept code has been published for this vulnerability. Treat unpatched systems as at risk.

Grav CMS 1.7.10 - Server-Side Template Injection (SSTI) (Authenticated)2021-06-07 · webapps · php

Impact

### Impact 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. ### Patches The issue was addressed by preventing dangerous functions from being called in Twig templates. A configuration option has been added to manually allow arbitrary PHP functions (`system.twig.safe_functions`) and filters (`system.twig.safe_filters`). Futures major versions of Grav may disable this functionality by default. ### Workarounds Blocking access to the `/admin` path from untrusted sources will reduce the probability of exploitation. ### References - https://portswigger.net/research/server-side-template-injection - https://blog.sonarsource.com/grav-cms-code-execution-vulnerabilities ### For more information If you have any questions or comments about this advisory, you can contact: - The original reporters, by sending an email to vulnerability.research [at] sonarsource.com; - The maintainers, by opening an issue on this repository.

Affected packages

Ecosystem	Package	Affected	Fixed in
composer	`getgrav/grav`	<= 1.7.10	1.7.11

Affected products

Vendor	Product	Affected versions
Getgrav	Grav	before 1.7.11

Weakness classification

CWE-94