Uncovering CVE-2021-4316: A Remote Attacker's Guide to Spoofing Browser UI in Google Chrome
Hello folks! Today, we're going to delve into an exciting and mildly alarming world of cyber vulnerability - specifically, CVE-2021-4316. We'll not only explore what this bug is all about, but we'll also take a look at how it works, its effects on the Cast UI in Google Chrome, and even get a chance to examine some code snippets.
CVE-2021-4316 deals with an inappropriate implementation in the Cast UI, which is part of Google Chrome, and issues that have been detected in versions prior to 96..4664.45. This vulnerability makes it possible for a remote attacker to spoof the browser UI by sending a cunningly crafted HTML page.
Before we dive into the details, let me first point you towards two important resources that will help you better understand and track this vulnerability:
1. Original CVE reference: CVE-2021-4316
2. Chromium Security Severity: Low
Now, let's get started by discussing the Cast UI and how it suffers from this inappropriate implementation.
Cast UI and Inappropriate Implementation
If you've ever used Google Chrome to cast a video to your TV, you've likely come across the Cast UI. The Cast UI allows users to connect their devices to nearby Chromecast-enabled devices. Unfortunately, CVE-2021-4316 takes advantage of a flaw in the way Cast UI is implemented to spoof the browser UI.
To understand how a vulnerability like this works, let's look at a simplified code snippet of a crafted HTML page that would exploit this flaw:
<!DOCTYPE html>
<html>
<head>
<style>
#cast-ui-frame {
width: 300px;
height: 100px;
visibility: hidden;
}
</style>
</head>
<body>
<div id="cast-ui-frame">
<iframe src="https://attacker-site.example.com/castui.html"></iframe>;
</div>
</body>
</html>
As you can see, this particular HTML page hosts an iframe with a width and height of 300x100 pixels, and its visibility is set to hidden. Inside the iframe, the attacker-site.example.com URL points to a specially crafted casting control page, which, when loaded, mimics the look of the Cast UI.
An attacker would then simply trick the user into interacting with the seemingly legitimate Cast UI, which might grant them access to sensitive information, such as Wi-Fi network details.
Exploiting the Vulnerability
Now that we've seen a code snippet of what an attacker could use, let's explore the steps on how it could happen:
The attacker creates a malicious webpage containing the CVE-2021-4316 exploit.
2. The targeted user visits the attacker's website (a phishing email could be an example of how they end up there) and is presented with a seemingly legit Cast UI.
3. Believing it's the real Chrome Cast UI, the user inadvertently grants the attacker access to sensitive data by initiating cast functionality.
Due to the nature of this vulnerability being able to spoof the browser UI, the Chromium security severity has been classified as low. However, it's still essential to take necessary precautions and ensure that your browser is updated to the latest version.
Mitigation and Conclusion
Luckily, Google acted quickly to address this vulnerability, and it has now been patched. Google Chrome users should update to the latest version (96..4664.45) to ensure their devices are no longer susceptible to this bug.
In conclusion, CVE-2021-4316 is a fascinating yet concerning vulnerability affecting the Cast UI in Google Chrome. While it's classified as a low-severity bug, it's a poignant reminder of how important it is to keep our software up to date and be vigilant about the websites and emails we interact with.
Stay safe out there, and make sure to keep your browsers updated!
Timeline
Published on: 07/29/2023 00:15:00 UTC
Last modified on: 08/02/2023 03:55:00 UTC