Yii 2 before 2.0.52 mishandles the attaching of behavior that is defined by an class array key, a CVE-2024-4990 regression, as exploited in the wild in February through April 2025.

A vulnerability, which was classified as critical, was found in yiisoft Yii2 up to 2.0.39. This affects the function Generate of the file phpunit\src\Framework\MockObject\MockClass.php. The manipulation leads to deserialization. It is possible to initiate the attack remotely. The exploit has been disclosed to the public and may be used.

A vulnerability, which was classified as critical, has been found in yiisoft Yii2 up to 2.0.45. Affected by this issue is the function getIterator of the file symfony\finder\Iterator\SortableIterator.php. The manipulation leads to deserialization. The attack may be launched remotely. The exploit has been disclosed to the public and may be used.

During the internal penetration testing of our product based on Yii2, we discovered an XSS vulnerability within the framework itself. This issue is relevant for the latest version of Yii2 (2.0.49.3).

Conditions for vulnerability reproduction

The framework is in debug mode (YIIDEBUG set to true). The php.ini setting zend.exceptionignoreargs is set to Off (default value). An attacker induces an exception in the application, leading to a stack trace page being displayed.

Vulnerability description

The issue lies in the mechanism for displaying function argument values in the stack trace. The vulnerability manifests when an argument's value exceeds 32 characters. For convenience, argument values exceeding this limit are truncated and displayed with an added "...". The full argument value becomes visible when hovering over it with the mouse, as it is displayed in the title attribute of a span tag. However, the use of a double quote (") allows an attacker to break out of the title attribute's value context and inject their own attributes into the span tag, including malicious JavaScript code through event handlers such as onmousemove.

Demonstration example: http://31.184.254.143/about/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa%22%20onmousemove=alert(1)%20style=%22width:%20100000px;%20height:%20100000px;%20position:%20absolute;%20top:%20-10000px;%20left:%200;%22

Impact of the vulnerability

This vulnerability allows an attacker to execute arbitrary JavaScript code in the security context of the victim's site via a specially crafted link. This could lead to the theft of cookies (including httpOnly cookies, which are accessible on the page), content substitution, or complete takeover of user accounts.

Technical analysis and mitigation suggestion

Upon analyzing the framework's source code, it was found that data handling for the title attribute is performed in the file framework/web/ErrorHandler.php. The identified problem is related to changes made in the commit https://github.com/yiisoft/yii2/commit/8cc9aeb2f0b2ffe02fb54a817064e9da75512706 , which led to the disabling of encoding for single and double quotes in the htmlEncode method (https://github.com/yiisoft/yii2/blob/8cc9aeb2f0b2ffe02fb54a817064e9da75512706/framework/web/ErrorHandler.php#L183) due to the addition of the ENTNOQUOTES flag. To address this issue while preserving the functionality intended by the commit, we suggest modifying the htmlEncode method as follows:

return htmlspecialchars($text, ENTQUOTES | ENTSUBSTITUTE | ENTHTML5, 'UTF-8');

This change will effectively prevent the XSS vulnerability while maintaining the targeted functionality of the previous changes.

Conclusion

Based on the above, we strongly recommend implementing the suggested changes to the project's main code as soon as possible to protect framework users from potential attacks. I am ready to provide further information or assistance, including creating a pull request if necessary.

yiisoft/yii before version 1.1.27 are vulnerable to Remote Code Execution (RCE) if the application calls unserialize() on arbitrary user input. This has been patched in 1.1.27.

yii2 is vulnerable to Use of Predictable Algorithm in Random Number Generator

yii2 is vulnerable to Use of Predictable Algorithm in Random Number Generator

Potential remote code execution in LUA context of the redis server via methods yii\redis\ActiveRecord::findOne() and ::findAll()

Possibility of manipulated condition when unfiltered input is passed to yii\elasticsearch\ActiveRecord::findOne() and ::findAll()

Potential SQL injection in methods yii\db\ActiveRecord::findOne() and ::findAll()

An XSS vulnerability exists in framework/views/errorHandler/exception.php in Yii Framework 2.0.12 affecting the exception screen when debug mode is enabled, because $exception->errorInfo is mishandled.