In early 2023, the cybersecurity world was rocked by news of CVE-2023-0129, a high-severity vulnerability found in Google Chrome’s Network Service. This flaw was present in Chrome versions before 109..5414.74 and allowed attackers to exploit heap buffer overflows through malicious browser extensions and tricked HTML content.

In this article, we’ll break down what CVE-2023-0129 is, how attackers could actually exploit it, look at a code sample, and see how Google responded. Whether you’re simply curious or want to keep your browser safe, this is your exclusive deep dive.

What is a Heap Buffer Overflow?

Imagine you have a box (the buffer) that fits five marbles (data). If you start putting more than five, the extra marbles spill into nearby boxes, possibly messing up other things in the process. In programming, a heap buffer overflow happens when a program writes more data to a buffer in the heap (a special area in memory) than it should.

If attackers can control what spills over, they can sometimes hijack the computer or browser.

Understanding CVE-2023-0129

CVE-2023-0129 exists in Chrome’s "Network Service"—the part handling network resources like webpages, APIs, and images.

If an attacker *tricked a user into installing a malicious Chrome extension*, they could interact with that extension using carefully crafted HTML (webpages) to make Chrome write more data than intended in its memory. This could lead to corrupted memory, browser crashes, or even worse, code execution—the attacker runs programs with your browser’s privileges.

#### Offical Write-up (Chrome's Release Notes):

> High CVE-2023-0129: Heap buffer overflow in Network Service. Reported by srodulv (Secsi) on 2022-12-09.
>
> *Heap buffer overflow in network service. A remote attacker who convinced a user to install a malicious extension could exploit heap corruption via crafted HTML page and specific interactions.*

Trigger the Exploit with Specially Crafted HTML

The malicious extension works with crafted web pages to send strange or oversized data to the Chrome Network Service.

Exploit Heap Corruption

The goal: break memory boundaries to potentially run arbitrary code or take over the browser session.

Example Attack Flow (Pseudocode)

We don’t have real exploit code (since it’s very dangerous), but here’s what a simplified version might look like, for educational understanding only:

1. Extension Permissions (malicious manifest.json)

{
  "name": "Evil Net Helper",
  "version": "1.",
  "manifest_version": 3,
  "permissions": ["webRequest", "webRequestBlocking", "http://*/*";, "https://*/*";],
  "background": {
    "service_worker": "background.js"
  }
}

2. Extension Background Script (abusing web requests)

// background.js

chrome.webRequest.onBeforeRequest.addListener(
  function(details) {
    // sends strange/large data to trip up the Network Service
    fetch("https://victim-site.com/api";, {
      method: "POST",
      body: "A".repeat(10000000) // overly large request data for overflow
    });
  },
  { urls: ["<all_urls>"] },
  ["blocking"]
);

3. Crafted HTML triggering the extension support

<!-- Attacker-controlled HTML page -->
<!DOCTYPE html>
<html>
<body>
  <script>
    // Initiates actions that make the extension send huge requests
    fetch("/api", { method: "POST", body: "trigger" });
  </script>
</body>
</html>

What Happens?

When Chrome’s Network Service tries to process the oversized or malformed data (sent through the malicious extension), it overflows its memory buffer—leading possibly to heap corruption.

Why It’s Dangerous

- The exploit chain relies on tricking users into installing an extension, which is easier than tricking them into downloading complex malware.
- Chrome’s sandbox security might help, but if heap corruption is pushed far enough, in some cases attackers could break free and run code.
- Heap buffer overflows are a popular class of vulnerabilities used for browser "jailbreaks" and serious attacks.

Patch and Fix

Google fixed CVE-2023-0129 in Chrome 109..5414.74.  
If you use Chrome, make sure you updated after January 10th, 2023.

> Official Chrome Release Note

References

- CVE-2023-0129 Details on MITRE
- Chrome Stable Channel Release Notes Jan 2023
- Chromium Bug Tracker ID (restricted access)
- Heap Buffer Overflow Overview by OWASP

Conclusion

CVE-2023-0129 is a powerful reminder that browsers are only as strong as their code and the extensions you grant access. Treat browser extensions as you would any installed app, and always keep Chrome up to date to avoid these vulnerabilities.

Timeline

Published on: 01/10/2023 20:15:00 UTC
Last modified on: 01/13/2023 15:02:00 UTC