CVE-2026-117896 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/28/2026
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 application continues to reference a block of memory that has already been deallocated by the system. In the context of web browser engines, such errors typically arise during complex DOM manipulation operations where elements are removed from the document tree or replaced with new nodes while references to those original objects remain active in JavaScript execution contexts or internal event handlers. When the garbage collector reclaims the memory associated with these detached DOM nodes, any subsequent attempt by the application logic to access properties or methods of that now-invalid pointer results in undefined behavior. This category of vulnerability is formally categorized under CWE-416, which defines use-after-free as a situation where software uses a pointer after it has been freed, leading to potential crashes, data corruption, or arbitrary code execution depending on how the memory allocator handles the reclaimed space and what an attacker can inject into that region.
The operational impact of this vulnerability is severe because browsers are designed to execute untrusted content from various web sources. An attacker could craft a malicious webpage containing specially constructed HTML and JavaScript payloads that trigger the specific sequence of DOM operations leading to the use-after-free condition. By carefully controlling the timing and allocation patterns, an adversary might be able to overwrite the freed memory with controlled data structures or shellcode before it is reused by another part of the browser process. This scenario aligns closely with MITRE ATT&CK technique T1203, which covers exploitation for client-side execution, as well as techniques related to memory corruption such as heap spraying often associated with CVE-2024-9680 and similar high-severity issues in rendering engines. Successful exploitation could allow a remote attacker to execute arbitrary code within the context of the victim's browser process, potentially leading to full system compromise if additional sandbox escape vulnerabilities are present or if the user has elevated privileges.
Mitigation for this vulnerability relies primarily on timely software updates as provided by Mozilla. The issue was resolved in Firefox version 159 and is also patched in the Extended Support Release channels at versions 115.44 and 153.6, ensuring that both standard users and enterprise environments running stable branches are protected against this specific memory corruption flaw. Organizations should enforce automated update policies to ensure all endpoints have applied these patches immediately upon availability. In addition to patching, defense-in-depth strategies such as enabling strict Content Security Policies can help mitigate the impact of potential exploitation by restricting inline script execution and limiting resource loading sources. Furthermore, keeping operating system-level protections like Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) enabled provides an additional layer of security that makes it significantly more difficult for attackers to reliably exploit memory corruption vulnerabilities even if they manage to trigger the underlying flaw in the browser engine.