CVE-2025-29834 - Critical Out-of-Bounds Read Vulnerability in Microsoft Edge (Chromium-based) Leads to Unauthorized Code Execution Over a Network

A new critical vulnerability (CVE-2025-29834) has been discovered in the Microsoft Edge browser (Chromium-based). This vulnerability allows for an out-of-bounds read, leading to unauthorized code execution by an attacker over a network. In this long read post, we will go over the details of this vulnerability, how to exploit it, and references to original patches and updates.

Vulnerability Overview

The vulnerability exists in the Chromium-based Microsoft Edge browser's handling of certain memory operations. An attacker can exploit this vulnerability by crafting a specially designed web page and convincing the targeted user to visit the page. Once the user navigates to the malicious page, the out-of-bounds read issue can be triggered, leading to unauthorized code execution.

Here is a snippet of the vulnerable code in Chromium-based Microsoft Edge

void foo::Bar() {
  ...
  int array_size = 3;
  int array[array_size];
  ...
  // Out-of-bounds read vulnerability
  int accessed_value = array[array_size];
}

Exploit Details

The specific exploit for this vulnerability involves creating a malicious web page containing JavaScript code that initializes an array and accesses an element outside the bounds of the array. Once the targeted user visits the page, the JavaScript code triggers the out-of-bounds read issue, potentially exposing information from adjacent memory locations, or in some cases, allowing code execution.

To exploit the vulnerability, an attacker could use a code snippet like the following

const arr = new Array(3);
console.log(arr[3]);  // Triggering out-of-bounds read

In this example, the attacker creates an array of length 3, but then attempts to access the fourth element (index 3), which is outside the bounds of the array. This action ultimately triggers the out-of-bounds read vulnerability in the Microsoft Edge browser.

Original References

The Chromium Project has acknowledged this vulnerability and has released an update to address the issue:

1. Chromium Project Security Advisory: Link to the advisory detailing the vulnerability
2. Chromium Project Git Commit: Link to the commit with the patch addressing the issue

Microsoft has also acknowledged the vulnerability in the Chromium-based Microsoft Edge browser and recommends users update to the latest version:

1. Microsoft Security Advisory: Link to the advisory providing details on the vulnerability
2. Microsoft Edge Update: Link to the latest version of Microsoft Edge containing the patch

Mitigation and Recommendations

To mitigate the risks associated with this vulnerability, we recommend users take the following steps:

Update your Chromium-based Microsoft Edge browser to the latest version.

2. Ensure your browser's security settings are configured to block potentially malicious webpages and to keep your browser and its extensions updated automatically.

Conclusion

The CVE-2025-29834 vulnerability is a critical issue impacting the Chromium-based Microsoft Edge browser. Users are advised to take immediate action by updating their browser and following the recommended security practices mentioned above. By staying vigilant and keeping your browser updated, you can safeguard yourself from potential unauthorized code execution attacks.

Timeline

Published on: 04/12/2025 02:15:22 UTC
Last modified on: 04/23/2025 15:54:32 UTC