CVE-2023-0141: Addressing Insufficient Policy Enforcement in CORS in Google Chrome

In the constantly evolving world of the internet, security vulnerabilities are an area of constant concern for both end-users and developers. One such vulnerability was recently discovered, affecting Google Chrome versions prior to 109..5414.74. Designated as CVE-2023-0141, this vulnerability deals with insufficient policy enforcement in Cross-Origin Resource Sharing (CORS) in Google Chrome, which allows a remote attacker to leak cross-origin data via a crafted HTML page. In this post, we will delve deeper into this vulnerability, its potential implications, and the steps taken to fix it in later Chrome versions.

Details About the Vulnerability

CVE-2023-0141 is classified as a security vulnerability with low severity according to Chromium security's assessment. It is related to Cross-Origin Resource Sharing (CORS), which refers to a mechanism that allows various web applications running on different domains to exchange data or resources. This functionality is critical for web developers to create seamless and interactive applications that can access data from multiple sources.

However, the vulnerability arises when CORS policies are not adequately enforced due to outdated or vulnerable code. In short, this allows a potentially malicious remote attacker to circumvent these policies and access cross-origin data through a crafted HTML page.

Code Snippet

To better understand how this vulnerability can manifest, consider the following example of an HTML page that an attacker may craft:

<!DOCTYPE html>
<html>
<head>
    <script>
        function corsLeak() {
            var xhr = new XMLHttpRequest();
            xhr.onreadystatechange = function() {
                if (xhr.readyState === XMLHttpRequest.DONE) {
                    if (xhr.status === 200) {
                        document.getElementById("leakedData").innerHTML = xhr.responseText;
                    }
                }
            }
            xhr.open("GET", "https://victim.example.com/sensitive-data";, true);
            xhr.withCredentials = true; // Required for authentication
            xhr.send();
        }
    </script>
</head>
<body>
    <button onclick="corsLeak()">Leak Data</button>
    <div id="leakedData"></div>
</body>
</html>

In the code snippet above, the attacker is using XMLHttpRequest to issue a GET request to a sensitive-data endpoint on the victim's domain. Due to the incorrect enforcement of CORS in Chrome prior to 109..5414.74, this request may still be successful, and the attacker can leak sensitive data to users who visit the malicious site hosting this page.

References

For original reports and further documentation on this vulnerability, refer to the following resources:

1. Google's Chrome Releases Blog Post detailing the update that fixes this issue.
2. The Official CVE-2023-0141 Entry on the MITRE website, which provides a brief overview of the vulnerability.
3. The Chromium Issue Tracker for a detailed analysis of the vulnerability and the patch that fixed it.

An attacker could potentially exploit this vulnerability by following this process

1. Set up a malicious website hosting the crafted HTML page (as demonstrated in the code snippet) designed to trigger a CORS request to the target site.
2. Lure unsuspecting users to visit the malicious website, which initiates a CORS request from their browser.
3. Capture the leaked cross-origin data and use it for further exploitation, identity theft, or other malicious activities.

Mitigation and Fixes

Thankfully, Google was quick to recognize and address this vulnerability. By updating to Google Chrome version 109..5414.74 or newer, users can ensure that they are not at risk from this particular issue. To verify the current version of Chrome, visit chrome://version in the browser's address bar. An update can be triggered through the browser settings or by visiting the official Chrome download page.

Conclusion

CVE-2023-0141 highlights the importance of continuous vigilance in software security, as even widely used products like Google Chrome can have vulnerabilities. While the severity of this particular issue is low, it serves as a reminder for users to keep their software up to date and remain cautious of potential exploitation risks. Developers should also be mindful of new updates and fixes, diligently reviewing and implementing them to ensure the optimal security of their applications.

Timeline

Published on: 01/10/2023 20:15:00 UTC
Last modified on: 01/13/2023 14:12:00 UTC