CVE-2026-117925 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 • 10/27/2026
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 software continues to reference a block of memory that has already been deallocated or freed by the system. In the context of browser rendering engines, such errors typically arise during complex interactions involving dynamic content manipulation, where elements are removed from the DOM tree while references to them remain active in JavaScript execution contexts or internal layout structures. When the garbage collector reclaims this memory for other purposes, any subsequent attempt by the application to access it results in undefined behavior, potentially leading to data corruption or arbitrary code execution if an attacker can carefully craft the freed memory contents and control the read operation.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow attackers to manipulate program flow through heap spraying techniques or by controlling what gets allocated into the previously freed space. If the browser reads from this stale pointer, it may interpret maliciously crafted data as executable code or valid object structures. This can lead to remote code execution with the privileges of the user running the browser. The vulnerability affects the core rendering and parsing logic, meaning that simply visiting a specially constructed webpage containing specific HTML elements combined with JavaScript triggers could exploit the flaw without requiring any additional plugins or extensions.
The operational impact of this vulnerability is severe, as it compromises the integrity and confidentiality of the browsing session. Successful exploitation allows an attacker to execute arbitrary code on the victim's machine, potentially leading to full system compromise depending on the user's privileges. This includes access to sensitive data stored in cookies, local storage, or browser history, as well as the ability to install malware or use the compromised device for further attacks within a network. The risk is amplified by the fact that such vulnerabilities are often found in widely used components like DOM and HTML parsing, which process untrusted input from virtually every website visited.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-416, Use After Free, which describes situations where a pointer references memory that has been freed or is no longer valid. In the context of modern cyber threat intelligence frameworks, this type of exploitation falls under MITRE ATT&CK technique T1203, Exploitation for Client Execution, specifically within the browser-based attack vector category. Attackers frequently leverage such flaws in web browsers to deliver payloads that bypass traditional security controls by exploiting trusted applications like Firefox to gain initial access or persistence on target systems.
To mitigate this risk, it is imperative to update Mozilla Firefox and all associated Extended Support Release versions immediately. The vulnerability was addressed in Firefox version 159, as well as the ESR branches at versions 115.44 and 153.6. Users should ensure that automatic updates are enabled or manually check for the latest patches through the browser's help menu. Additionally, organizations relying on these browsers for enterprise environments should verify deployment configurations to enforce timely patching across all endpoints. While no specific workarounds exist beyond updating, employing strict content security policies and disabling unnecessary JavaScript execution in untrusted contexts can reduce the attack surface by limiting the ability of malicious scripts to trigger complex DOM manipulations that might expose such memory management flaws.