CVE-2026-117932 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security issue represents a critical memory management flaw within the Document Object Model, specifically affecting the core and HTML components of the browser engine. A use-after-free vulnerability occurs when software continues to reference a pointer after it has been freed or deallocated from system memory. In this specific context, the DOM implementation failed to properly manage the lifecycle of internal objects associated with HTML elements. This typically happens during complex interactions involving dynamic content manipulation, where an object is destroyed while still being referenced by another part of the application logic. When the browser attempts to access these freed memory regions through dangling pointers, it violates fundamental memory safety principles, leading to undefined behavior that can be exploited for malicious purposes.
From a technical perspective, this flaw allows attackers to craft specific web pages or scripts that trigger the premature deallocation of DOM nodes while other processes retain references to them. By carefully controlling the timing and sequence of these operations, an attacker can manipulate how the browser interprets the freed memory contents. This manipulation enables arbitrary code execution on the victim's machine under the context of the affected application. The vulnerability is particularly dangerous because it resides in core rendering components that are invoked frequently during normal browsing activities, increasing the likelihood of successful exploitation against users who visit maliciously crafted sites or click on compromised links.
The operational impact of this vulnerability extends beyond simple data corruption to full system compromise. An attacker leveraging this use-after-free condition can execute arbitrary code with the privileges of the user running the browser. This means that sensitive information such as login credentials, financial details, and personal communications stored locally by the browser could be exfiltrated. Furthermore, the compromised machine may serve as a foothold for further network attacks, including lateral movement within corporate environments or installation of persistent malware backdoors. The severity is amplified by the fact that DOM vulnerabilities are often difficult to detect through standard antivirus solutions because they rely on sophisticated memory corruption techniques rather than known malicious signatures.
Industry standards classify this type of flaw under CWE-416, which denotes Use After Free errors in software development. These errors are consistently ranked among the most dangerous programming mistakes due their potential for remote code execution and stability disruption. In terms of offensive security frameworks, such as MITRE ATT&CK, this vulnerability aligns with techniques related to memory corruption exploitation and potentially command-and-control activities if used to establish persistent access. The attack vector is primarily classified as network-based or local depending on how the malicious content is delivered, but it fundamentally relies on social engineering or drive-by download tactics to get a victim to load the exploit code within their browser session.
Mitigation strategies for this vulnerability are straightforward and have already been implemented by the vendor. Users must update Firefox to version 159 or later, including the Extended Support Release (ESR) version 153.6, which contains the necessary patches to correct the memory management logic in the DOM components. These updates include rigorous checks to ensure that pointers are nullified after deallocation and prevent access to freed memory regions. For organizations managing large fleets of browsers, it is critical to automate patch deployment processes to minimize exposure windows. Additionally, implementing browser hardening techniques such as disabling JavaScript for untrusted sites or using content security policies can provide an additional layer of defense against exploitation attempts while waiting for full patch propagation across all endpoints.