CVE-2026-118013 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Layout: Images, Video, and HTML Frames component. This vulnerability was fixed in Firefox 159.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability represents a critical memory management error within the rendering engine of Mozilla Firefox, specifically located in the subsystem responsible for handling layout operations involving images, video elements, and HTML frames. As a use-after-free flaw, this defect arises when the application attempts to access memory that has already been deallocated by the system. In complex web environments where dynamic content is frequently loaded and removed, such as pages with embedded media or iframe structures, the browser must meticulously track object lifecycles. When this tracking fails due to a logic error in the layout engine, pointers may continue to reference freed memory blocks rather than being nullified or updated correctly. This scenario creates an opportunity for attackers to manipulate the state of the application by writing arbitrary data into these dangling pointers before they are reallocated for other purposes, potentially leading to code execution with the privileges of the user running the browser.
From a technical perspective, this flaw falls under the Common Weakness Enumeration category CWE-416, which defines use-after-free conditions as a result of improper invalidation of references after memory release. The vulnerability likely stems from race conditions or incorrect reference counting mechanisms within the Layout: Images, Video, and HTML Frames component. When an image is unloaded or a frame is removed from the DOM tree, the associated layout objects must be properly destroyed and their pointers cleared. If the browser retains a reference to these objects while they are being freed elsewhere in the memory management subsystem, subsequent operations that rely on those references will interact with invalid memory addresses. This can lead to crashes, data corruption, or more severe exploitation vectors where an attacker crafts malicious HTML content containing specially constructed media elements to trigger the premature deallocation and subsequent access of these layout structures during page rendering.
The operational impact of this vulnerability is significant because it affects a core component of web browsing that handles high-frequency interactions with multimedia content. Users visiting compromised websites or pages injected with malicious scripts could experience denial-of-service conditions through application crashes, which disrupts productivity and system stability. More critically, if the use-after-free condition can be reliably triggered and exploited, it allows for arbitrary code execution on the victim's machine. This compromises the integrity of the user environment, potentially leading to data theft, installation of malware, or further lateral movement within a networked environment. The presence of this flaw in Firefox versions prior to 159 means that any system running these older builds is exposed to risks associated with modern web-based attacks targeting browser rendering engines.
Mitigation strategies primarily involve ensuring that the Mozilla Firefox application is updated to version 159 or later, where the developers have implemented fixes for the memory management logic in the affected component. Organizations should enforce automated patching policies to maintain up-to-date software versions across all endpoints. Additionally, users can employ browser hardening techniques such as disabling JavaScript on untrusted sites or using content security policies that restrict inline scripts and external resource loading from unknown origins. Security monitoring solutions should also be configured to detect anomalous behavior associated with memory corruption attempts, although the most effective defense remains timely application of vendor-provided patches to eliminate the underlying code defect entirely.