CVE-2026-92028 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified vulnerability represents a critical memory management error within the Document Object Model core and HTML components of Mozilla Firefox browsers. Specifically classified as an use-after-free condition, this flaw occurs when the browser's internal pointers continue to reference a block of memory that has already been deallocated or freed by the system. In complex web rendering engines like Gecko, which powers Firefox, the DOM is frequently manipulated through dynamic content updates, script execution, and style recalculations. When these operations occur rapidly or in specific edge cases involving nested elements or detached nodes, the internal state tracking may fail to invalidate references correctly. This results in a scenario where subsequent code attempts to read from or write to memory addresses that are no longer valid for the current object instance. Such conditions are particularly dangerous because they bypass standard safety checks designed to prevent access to uninitialized or recycled memory regions.
From a technical perspective, this flaw falls under CWE-416, which defines use-after-free as accessing memory after it has been freed. The operational impact of such vulnerabilities is severe and multifaceted. An attacker who can craft a malicious webpage containing specific HTML structures combined with JavaScript triggers could exploit this race condition or logic error to execute arbitrary code on the victim's machine. By carefully controlling the contents of the freed memory, an attacker might achieve remote code execution, leading to full system compromise. Alternatively, even if direct code execution is mitigated by modern browser security features like ASLR and DEP, the vulnerability can still be leveraged for denial-of-service attacks causing crashes or potentially for information disclosure where sensitive data residing in adjacent memory blocks could be leaked. The complexity of DOM manipulation makes these bugs difficult to detect through static analysis alone, often requiring sophisticated fuzzing techniques during development to uncover such timing-dependent errors.
Mitigation strategies primarily rely on the timely application of vendor patches. Mozilla has addressed this specific issue by updating their internal reference counting mechanisms and ensuring that pointers are nullified immediately upon object destruction within the DOM core. Users must upgrade to Firefox version 156, or if relying on extended support releases, update to ESR versions 115.41, 140.16, or 153.3 respectively. These updates contain the necessary code fixes that prevent the dangling pointer from being accessed after the associated memory has been released. Beyond patching, defense-in-depth measures such as enabling strict Content Security Policies can help mitigate potential exploitation by restricting inline script execution and limiting resource loading sources. Additionally, keeping browser plugins and extensions updated is crucial as they often interact with DOM elements and could serve as an attack vector if vulnerable components are exposed through third-party code.
In the context of broader cybersecurity frameworks, this vulnerability aligns with MITRE ATT&CK technique T1203, which covers exploitation for client-side execution. The use-after-free mechanism serves as a common primitive in exploit chains aimed at bypassing browser sandbox boundaries. Security teams should prioritize monitoring for indicators of compromise related to memory corruption events and ensure that automated patch management systems are configured to deploy these specific Firefox updates across all endpoints promptly. Regular vulnerability scanning and penetration testing focused on web application interactions with the DOM can also help identify similar implementation flaws in custom enterprise applications before they are exploited by threat actors leveraging public exploit kits.