Chrome is one of the most popular web browsers in the world, trusted by billions for everyday browsing. But, like any complex software, it isn’t immune to bugs—some of which can become major security threats. One such bug is CVE-2022-3311, a "use-after-free" vulnerability in Chrome’s import functionality, discovered and patched before Chrome version 106..5249.62.
This post will help you understand what this bug is, how an attacker might exploit it, and why it matters, all in simple terms. We’ll include code examples, links to key references, and step-by-step detail—so you don’t need to be a security pro to follow along.
Affects: Google Chrome (before 106..5249.62)
- Impact: Allows a remote attacker, after compromising a WebUI process, to escape the browser sandbox with a crafted HTML page
What is a Use-After-Free (UAF) Vulnerability?
A use-after-free happens when a program continues to use a part of memory ("object") after it has been "freed," or marked as available for reuse. If an attacker can manipulate this situation, they can potentially take control of what should be invalid memory, letting them run code, crash the program, or even break out of browser isolation.
How CVE-2022-3311 Happens in Chrome
In Chrome, WebUI is used for rendering browser-internal pages (like settings or extensions). The browser has strict sandboxing—isolating web content from the rest of your computer. But a bug in how Chrome handled the import API (specifically, importing modules or scripts) meant that a malicious site could put Chrome in a bad state:
The page triggers the freeing (deallocation) of an import-related object.
2. Without appropriate checks, Chrome tries to use this object again (it's "dangling"—pointing to freed space).
3. An attacker can now try to prepare (or "spray") that freed memory with something under their control, leading to unexpected code execution or a sandbox escape.
Realistic Exploit Scenario
Important: While there’s no widely circulated public exploit code for this exact bug, here’s a step-by-step hypothetical workflow showcasing how such a vulnerability could be exploited.
Suppose an attacker already has code running in a WebUI process (which might be achieved via a separate logic flaw or Cross-Site Scripting in an internal Chrome page, like chrome://downloads).
Trigger Use-After-Free with Malicious HTML
The attacker crafts an HTML page that loads a module dynamically and then removes references unexpectedly:
async function triggerUAF() {
let mod = await import('data:text/javascript,export let x=42;');
// Simulate freeing the object early
mod = null;
// Force garbage collection (not guaranteed, but can be attempted)
}
// Try to access the module again: use-after-free!
// (In real-world attacks, more precise memory manipulation is done)
triggerUAF();
Heap Spraying
Attackers fill memory ("heap spraying") so that, if the use-after-free is triggered, the browser’s old pointer might now point to their carefully prepared data. This can, in theory, allow remote code execution or, in this case, a sandbox escape—letting the attacker break out of the safe area and interact with your system, steal files, etc.
Sandbox Escape
If successful, the exploit can now run code outside the restricted environment. In the real world, this is often chained with other browser bugs for a bigger attack.
Note: Achieving a reliable exploit is complex and requires deep skills in browser internals and memory management. For this specific CVE, Google rates the severity as Medium because it requires further conditions (like already having code running in a WebUI process).
Google’s Chrome Release Notes:
(Note: Some entries may be private for security reasons)
Mitre CVE Page:
About Use-After-Free
How Was It Fixed?
The Chromium team patched the bug by ensuring the import logic correctly handles and tracks object lifetimes, preventing any use after they are freed.
If you want to see what changed, check the Chromium source code diffs for version 106.
Update Chrome:
If you haven’t already, update to the latest Chrome version. Chrome 106..5249.62 and newer are safe from this bug.
Beware Untrusted Pages:
Always be careful visiting unfamiliar links, especially those claiming to interact with browser-internal pages.
Keep Extensions Updated:
Since Chrome's WebUI is sometimes exposed to extensions, make sure your extensions are from a trusted source.
Conclusion
CVE-2022-3311 is a great example of how a seemingly small object-lifetime bug can have big security consequences in a modern browser. Thanks to the Chrome security team and responsible researchers, these bugs get found and fixed fast—but stay vigilant and keep your software updated.
> Want to learn more? <br>> Follow the Chrome security blog for future updates and in-depth writeups.
*This post is original and written exclusively for this request. For further questions or deep dives into browser exploitation, feel free to comment or reach out.*
Timeline
Published on: 11/01/2022 20:15:00 UTC
Last modified on: 12/09/2022 15:49:00 UTC