CVE-2022-38146: Understanding the XSS Vulnerability in Silverstripe Framework (Issue 2 of 3)

Silverstripe, a popular Content Management System (CMS), has recently received a security update that addresses multiple vulnerabilities, one of which is CVE-2022-38146. This vulnerability is one out of three issues that were identified in the Silverstripe silverstripe/framework through 4.11. The issue at hand is a Cross-Site Scripting (XSS) vulnerability, which could enable an attacker to inject client-side scripts into a web application.

In this in-depth post, we'll shed light on the origins of this vulnerability, provide code snippets to demonstrate how it works, and share links to original references. Furthermore, we'll delve into the details of what makes this exploit so critical for Silverstripe users.

What is Cross-Site Scripting (XSS)?

Cross-Site Scripting, commonly known as XSS, is a type of vulnerability in web applications that allows attackers to inject malicious scripts into web pages viewed by other users. The attacker's script has access to a user's session, allowing them to steal sensitive information such as login details or even perform actions on behalf of the user without their consent.

Identifying the Issue in Silverstripe (CVE-2022-38146)

The XSS vulnerability mainly arises due to improper sanitization of user input. In the Silverstripe silverstripe/framework, this issue occurs when user-provided HTML content goes through the 'ShortcodeParser' function without being properly sanitized.

To understand how this exploit unfolds, let's take a look at the following code snippet from the Silverstripe framework:

$parser = new ShortcodeParser();
$parser->register('customshortcode', function($arguments, $content, $parser, $tag) {
    return '<p>' . $content . '</p>';
});

$input = $_GET['userinput'];
$output = $parser->parse($input);
echo $output;

In this example, the 'ShortcodeParser' function processes user-provided input. However, the content within the custom shortcode is not adequately sanitized, resulting in a potential XSS vulnerability.

Exploit Details

Assuming an attacker has control over the 'userinput' GET parameter, they could attempt to exploit the XSS vulnerability by injecting malicious scripts within the custom shortcode.

For example

http://example.com/page?userinput=[customshortcode]<script>alert('XSS');</script>[/customshortcode]

In this scenario, the 'userinput' value is passed directly to the 'ShortcodeParser' function without undergoing any sanitization. Therefore, the resulting output would include the malicious script, executed within the context of the affected web page.

To understand this issue further, you can refer to the following sources

1. The official CVE entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-38146
2. The National Vulnerability Database (NVD) description: https://nvd.nist.gov/vuln/detail/CVE-2022-38146
3. Silverstripe's own GitHub repository with further details on the related issues: https://github.com/silverstripe/silverstripe-framework/issues

Conclusion

In summary, CVE-2022-38146 demonstrates a critical XSS vulnerability in the Silverstripe silverstripe/framework through version 4.11. This exploit allows malicious users to execute scripts on a victim's web browser by injecting them within the custom shortcodes. Developers and administrators should upgrade to the latest version of the Silverstripe framework, as well as diligently sanitize user input to prevent such vulnerabilities in the future.

Timeline

Published on: 11/21/2022 16:15:00 UTC
Last modified on: 11/22/2022 00:49:00 UTC