Cybersecurity continues to be a pressing concern for the industry as attackers uncover new vulnerabilities. Google Chrome, one of the most popular web browsers, has had its fair share of security issues. Among the recently discovered vulnerabilities in Chrome is the CVE-2023-2929, which relates to an out-of-bounds write in SwiftShader affecting versions prior to 114..5735.90. A successful exploitation of this vulnerability could result in heap corruption by a remote attacker through a crafted HTML page. According to Chromium's security team, this vulnerability has a high severity rating.

In this post, we will dive into the details of CVE-2023-2929, including the code snippet involved, original references, exploit specifics, and mitigation steps for users and developers.

The following code snippet demonstrates an example of the vulnerable code in SwiftShader

// Unsafe code in SwiftShader - vulnerability exists in the array access

void SwsShader::processPixelData()
{
    int index = getIndexFromData(); // Obtain index from pixel data

    if (index >= ) {
        pixelData[index] = modifyPixel(pixelData[index]);
    }
}

In this example, the code is susceptible to an out-of-bounds write because it doesn't thoroughly check the value of the index variable. As a result, the pixelData array could potentially be accessed and modified outside its boundaries, causing heap corruption.

Original References

The details of the vulnerability can be tracked on Chromium's official bug report, which can be found at:

- Issue 1326744: Heap corruption vulnerability in SwiftShader

Exploit Details

An attacker could exploit the vulnerability by creating a malicious HTML page containing a specially crafted WebGL shader code that would trigger the vulnerability and bypass the browser's security measures. By enticing a user to open the malicious page, the attacker could introduce heap corruption into the Chrome process.

The attacker could use this to execute arbitrary code on the user's system, breach user privacy, or server objectives like compromising credentials or installing malware. A typical exploit scenario would involve an attacker hosting the malicious page on their website or injecting the malicious WebGL code into an existing web page via cross-site scripting (XSS) attacks.

Mitigation Steps

1. Update Chrome: As a user, the foremost step should be to update your Google Chrome to the latest version (114..5735.90 or later) as the vulnerability affects versions before that. By doing so, you can protect your browser against the CVE-2023-2929 vulnerability and potential attacks.

2. Safe browsing habits: Always be cautious when browsing online, and avoid visiting untrusted websites or clicking suspicious links. Do not interact with unexpected emails or pop-ups that direct you to unknown websites.

3. Developers: If you work on projects that use SwiftShader, ensure that you implement proper bounds checking in your code to prevent out-of-bounds writes. For example, the vulnerable code snippet could include checks like:

// Improved, safe code with bounds checking
void SwsShader::processPixelData()
{
    int index = getIndexFromData(); // Obtain index from pixel data

    if (index >=  && index < array_size(pixelData)) {
        pixelData[index] = modifyPixel(pixelData[index]);
    }
}

Conclusion

CVE-2023-2929 is a high-severity heap corruption vulnerability in the SwiftShader of Google Chrome. By exploiting this vulnerability, an attacker could execute arbitrary code on the victim's system by tricking them into opening a crafted HTML page. To stay protected, ensure that you update your browser to the latest version, follow safe browsing practices, and maintain caution when dealing with unfamiliar web pages and emails.

Timeline

Published on: 05/30/2023 22:15:00 UTC
Last modified on: 06/04/2023 04:15:00 UTC