Summary: The Firefox browser has been found to be vulnerable to an out-of-bounds read in certain low-memory situations, which could lead to an exploitable crash while parsing HTML with the DOMParser utility. This vulnerability impacts Firefox versions prior to 116, Firefox ESR before 102.14, and Firefox ESR before 115.1.


A recent CVE advisory (CVE-2023-4048) has identified a critical security vulnerability in the Firefox web browser when parsing HTML with the DOMParser tool in low memory environments. This out-of-bounds read can result in a crash that can potentially be exploited by an attacker to compromise the affected system.

The Mozilla Foundation has addressed this issue by releasing updates for Firefox and Firefox ESR, and users are strongly advised to update their browsers to the latest, patched versions. This post outlines the details of this vulnerability, provides a code snippet to demonstrate the issue, and offers references to the original advisory and other relevant resources.

Exploit details

The vulnerability lies in the DOMParser implementation, which is used for parsing and processing HTML content. In certain low-memory situations, the parser can perform an out-of-bounds read, causing a crash. This crash can then potentially be exploited by an attacker to execute arbitrary code and gain unauthorized access to the system.

Firefox ESR < 115.1

To protect against this vulnerability, users should immediately update their browsers to the latest versions:

Code snippet

The following code snippet demonstrates the use of the DOMParser utility to parse and process HTML content in JavaScript:

const parser = new DOMParser();
const html = '<html><head><title>CVE-2023-4048</title></head><body>Exploitable crash in DOMParser</body></html>';
const doc = parser.parseFromString(html, 'text/html');

console.log(doc.title); // CVE-2023-4048
console.log(doc.body.textContent); // Exploitable crash in DOMParser

In a low memory situation, the DOMParser may encounter an out-of-bounds read while processing an HTML string, resulting in a crash. This crash can be exploited by an attacker to execute arbitrary code on the affected system.

For more information about this vulnerability, please consult the following resources

1. CVE-2023-4048 - The official CVE advisory detailing the vulnerability.

2. Mozilla Foundation Security Advisory 2023-03 - The security advisory from the Mozilla Foundation, which provides additional information and recommendations for users.

3. Mozilla Firefox Release Notes - The release notes for the latest versions of Firefox, which include patches for this vulnerability.


The DOMParser vulnerability in Firefox (CVE-2023-4048) is a serious security issue that can lead to exploitable crashes in low memory situations. Users should immediately update their browsers to the latest, patched versions in order to protect themselves from potential attacks. By staying informed about security vulnerabilities and ensuring that software is up to date, users can minimize the risk of being exploited by attackers.


Published on: 08/01/2023 15:15:00 UTC
Last modified on: 08/11/2023 20:03:00 UTC