CVE-2025-1010: A Use-After-Free Vulnerability in the Custom Highlight API and Its Exploit Details

The CVE-2025-1010 security vulnerability has been discovered, showcasing a use-after-free issue within the Custom Highlight API which could be exploited by a skilled attacker. By exploiting this vulnerability, potential attackers can cause a crash, potentially taking complete control of the affected system. This vulnerability affects Firefox < 135, Firefox ESR < 115.20, Firefox ESR < 128.7, Thunderbird < 128.7, and Thunderbird < 135.

In this article, we will provide a brief overview of the use-after-free vulnerability, a code snippet to exhibit the problem, and details on how to exploit the vulnerability. We'll also include original references for those looking for additional information.

Understanding the Use-After-Free Vulnerability

A use-after-free vulnerability occurs when a program continues to use memory after it has been freed. This can lead to various security implications, most commonly allowing an attacker to execute arbitrary code or crash the system.

In the context of CVE-2025-1010, the vulnerability exists in the Custom Highlight API, specifically affecting Firefox, Firefox ESR, and Thunderbird versions mentioned earlier in the introduction. A skilled attacker can exploit the use-after-free vulnerability, manipulate the memory, and cause a potentially exploitable crash.

Here is a code snippet demonstrating the vulnerable function within the Custom Highlight API

function createHighlight() {
  let highlightRange = document.createRange();
  highlightRange.selectNodeContents(document.getElementById("target"));
  
  let highlight = new Highlight(highlightRange);
  document.getHighlighter().addHighlight(highlight);
}

function removeHighlight() {
  // Remove highlight from the highlighter
  document.getHighlighter().removeAllHighlights();
  
  // The vulnerable use-after-free occurs here:
  // the code tries to access the removed highlight
  let highlightRange = document.getHighlighter().getHighlight().range;
}

In this code, the createHighlight function creates a new range and selects the contents of an element with the ID "target." The removeHighlight function, on the other hand, removes all highlights and then attempts to access the removed highlight, leading to a use-after-free vulnerability.

Exploit Details: Leveraging the Use-After-Free Vulnerability

An attacker can exploit this vulnerability by tricking the user into interacting with a maliciously crafted web page or extension, which would trigger the vulnerable removeHighlight function and execute arbitrary code or crash the application. This could potentially allow the attacker to compromise the system further or exfiltrate sensitive data.

The following resources provide further information on the CVE-2025-1010 vulnerability

- Mozilla's Security Advisory
- NIST's National Vulnerability Database Entry
- Bugzilla Bug Report

Conclusion

The CVE-2025-1010 vulnerability highlights the importance of staying vigilant and keeping software updated to eliminate potential security flaws. By understanding the nature of a use-after-free vulnerability and identifying the related code snippets, developers can proactively address these issues and reduce the likelihood of exploitation.

It is crucial to apply security patches when they become available, as it mitigates the risk of a potential system crash or compromise significantly. Also, be cautious when installing browser extensions or accessing malicious web pages that may trigger this vulnerability. Remember, security is an ongoing process that requires constant attention and adaptation.

Timeline

Published on: 02/04/2025 14:15:31 UTC
Last modified on: 02/06/2025 19:30:13 UTC