CVE-2026-117983 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Graphics 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 vulnerability represents a critical memory management error classified as an out-of-bounds write, specifically manifesting through a use-after-free condition within the graphics subsystem of Mozilla Firefox. This type of flaw occurs when the application attempts to access or modify memory that has already been deallocated by the system's garbage collector or explicit free operations. In the context of browser-based rendering engines such as Gecko, which handles complex graphical computations for web content, this error typically arises during the lifecycle management of graphics objects like textures, buffers, or compositor layers. When a reference to an object is retained after its underlying memory has been released, subsequent access by the renderer can lead to unpredictable behavior, including data corruption, application crashes, or potentially arbitrary code execution if an attacker can control the contents of the freed memory region and force their way into it before reallocation.
From a technical perspective, this vulnerability exploits the asynchronous nature of modern web rendering pipelines where objects may be destroyed on one thread while being accessed on another, such as the main UI thread versus the compositor or GPU process threads. The lack of proper synchronization mechanisms or reference counting errors allows stale pointers to remain valid in memory maps even after the resources they point to have been reclaimed. This creates a window of opportunity for exploitation where maliciously crafted web content can trigger specific rendering paths that result in the use-after-free condition. Such conditions are particularly dangerous because they bypass many traditional security boundaries, allowing an attacker to manipulate heap structures and potentially achieve remote code execution with the privileges of the user running the browser.
The operational impact of this vulnerability is severe, as it enables a remote attack vector where visiting a specially crafted webpage can lead to compromise of the victim's system. Attackers could leverage this flaw to execute arbitrary commands, install malware, or exfiltrate sensitive data stored within the browser context, such as cookies and session tokens. The presence of this issue in both standard Firefox releases and Extended Support Release (ESR) versions indicates that it affects a broad spectrum of users, including enterprise environments where stability and security are paramount. The exploitation potential is heightened by the fact that graphics processing often involves direct interaction with hardware accelerators and low-level system APIs, increasing the attack surface for privilege escalation or sandbox escape attempts.
To mitigate this risk, immediate action must be taken to update all instances of Firefox to version 159 or later, as well as any systems running Firefox ESR to version 153.6 or newer. These updates contain patches that enforce stricter memory safety checks and improve the lifecycle management of graphics objects within the rendering engine. Organizations should prioritize patching their endpoints through automated deployment tools to ensure uniform protection across all user devices. Additionally, security teams should monitor for indicators of compromise related to browser-based exploits and consider implementing application control policies or sandboxing solutions to limit the potential impact if a similar vulnerability were discovered in unpatched systems. Regular updates remain the most effective defense against such memory corruption vulnerabilities, which are increasingly common targets for advanced persistent threats seeking initial access vectors through web browsers.
This incident aligns with Common Weakness Enumeration (CWE) identifier CWE-416, Use After Free, and is relevant to MITRE ATT&CK technique T1203, Exploitation for Client Execution, where attackers utilize vulnerabilities in client software to execute malicious payloads on the target system. The resolution underscores the importance of maintaining up-to-date browser versions to protect against sophisticated web-based attacks that exploit low-level memory management flaws.