CVE-2026-92042 in Firefox
Summary
by MITRE • 09/15/2026
Race condition in the DOM: Content Processes component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified vulnerability represents a race condition within the Document Object Model implementation of Mozilla Firefox, specifically affecting the content processes architecture. In modern browser engines, particularly those utilizing multi-process isolation like Gecko, the DOM is managed across multiple threads to maintain responsiveness and security boundaries between different web pages or tabs. A race condition in this context implies that there exists an exploitable timing window where operations on shared data structures are not properly synchronized. This lack of atomicity allows for a scenario where one process attempts to read or modify state while another process is simultaneously altering it, leading to unpredictable behavior such as use-after-free errors, memory corruption, or logic bypasses. The specific component involved handles the parsing and manipulation of HTML content, which is critical for rendering web pages correctly and securely.
From a technical perspective, race conditions in DOM processing often stem from improper locking mechanisms or asynchronous operations that do not account for concurrent access patterns. When a user navigates to a maliciously crafted webpage, an attacker can trigger specific sequences of events designed to exploit this timing gap. By carefully crafting the payload to execute at precise moments during page load or script execution, it may be possible to manipulate internal pointers or state variables before they are updated by other threads. This could potentially lead to arbitrary code execution if the browser's sandboxing mechanisms fail due to the corrupted memory state, although typically such vulnerabilities result in cross-site scripting vectors or denial of service conditions depending on how the race is exploited and what resources are affected.
The operational impact of this vulnerability varies based on whether it can be successfully leveraged for remote code execution or if it remains limited to local effects like crashes or data leakage. If an attacker can exploit the race condition effectively, they might bypass same-origin policies, inject malicious scripts into trusted contexts, or crash the browser process causing a denial of service. Given that Firefox employs strict sandboxing for content processes, successful exploitation would likely require chaining this vulnerability with another flaw to escape the sandbox and gain higher privileges on the host system. However, even without full privilege escalation, such vulnerabilities undermine user trust by allowing potential data theft through cross-site scripting or session hijacking if cookies or local storage are accessible during the race window.
Mitigation for this issue has been addressed in Firefox version 156 and Firefox Extended Support Release (ESR) version 153.3. Users should immediately update their browsers to these patched versions to eliminate the vulnerability from their environment. For organizations managing large fleets of devices, it is recommended to enforce automatic updates or deploy patch management solutions that prioritize security fixes for browser components. Additionally, implementing Content Security Policy headers on web applications can help mitigate potential exploitation attempts by restricting script sources and reducing the attack surface available to attackers attempting to leverage DOM manipulation flaws.
This vulnerability aligns with CWE-362, which describes concurrent execution race conditions where software performs multiple operations simultaneously without proper synchronization. It also relates to ATT&CK technique T1059, Command and Scripting Interpreter, as exploitation could involve executing arbitrary scripts within the browser context. Furthermore, it touches upon aspects of CWE-416, Use After Free, if the race condition leads to accessing memory that has already been deallocated due to improper state management during concurrent DOM updates. Understanding these classifications helps in assessing the severity and developing more robust defensive strategies against similar concurrency bugs in web browsers and other complex software systems.