CVE-2026-117934 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Layout 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 classified as an out-of-bounds write due to use-after-free conditions within the Layout component of Mozilla Firefox browsers. This specific flaw arises when the application attempts to access or manipulate memory that has already been deallocated, leading to undefined behavior and potential system compromise. The issue was addressed in Firefox version 159, as well as in the Extended Support Release versions 115.44 and 153.6, indicating a targeted patch for this specific code path within the rendering engine responsible for processing web content layout structures.
From a technical perspective, use-after-free vulnerabilities occur when a pointer continues to be used after the memory it points to has been freed. In the context of browser engines like Gecko or WebKit derivatives used in Firefox, the Layout component handles the positioning and sizing of elements on a webpage. If an object representing a layout node is destroyed while references to it remain active within the event loop or rendering pipeline, subsequent operations may write data to arbitrary memory locations. This can corrupt internal data structures, overwrite function pointers, or alter control flow mechanisms, thereby providing an attacker with a mechanism for code execution.
The operational impact of this vulnerability is severe, as exploitation typically allows remote attackers to execute arbitrary code on the victim's system by crafting malicious web content that triggers the specific sequence leading to the use-after-free condition. Attackers could potentially bypass modern security mitigations such as heap randomization and stack canaries if they successfully control the memory layout post-deallocation. This aligns with common exploitation techniques observed in advanced persistent threats targeting browser engines, where precise memory corruption is leveraged to achieve arbitrary read-write primitives.
This vulnerability maps directly to Common Weakness Enumeration identifier CWE-416, which describes use-after-free errors. In terms of offensive security frameworks, the exploit chain likely involves steps categorized under MITRE ATT&CK technique T1203, specifically exploitation for client execution via browser or web application attacks. The attack vector is primarily network-based and requires user interaction to load a maliciously crafted webpage that triggers the flawed layout processing logic within the browser engine.
Mitigation strategies focus on ensuring timely updates to the affected software versions. Organizations should immediately patch all instances of Firefox 159, ESR 115.44, and ESR 153.6 or later to eliminate this specific code path vulnerability. Additionally, deploying content security policies can help restrict the types of scripts that execute within browser contexts, reducing the likelihood of successful exploitation even if similar vulnerabilities exist in other components. Security teams should also monitor for indicators of compromise related to memory corruption events and ensure that endpoint detection systems are configured to flag unusual heap activity associated with browser processes.