CVE-2026-84123 in Firefox
Summary
by MITRE • 09/01/2026
Privilege escalation due to use-after-free in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 155 and Firefox ESR 153.2.
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Analysis
by VulDB Data Team • 09/01/2026
The identified security flaw resides within the Graphics subsystem, specifically affecting the WebGPU implementation in Mozilla Firefox browsers. As a critical interface for modern web-based graphics rendering, WebGPU allows web applications to access low-level GPU functionality with improved performance and safety over previous APIs like WebGL. The vulnerability is classified as an use-after-free error, which represents one of the most dangerous classes of memory corruption bugs. This type of flaw occurs when program execution continues to reference a memory location after it has been freed or deallocated by the system. In the context of WebGPU, this likely involves internal data structures managing GPU resources such as textures, buffers, or shader programs where pointers are not properly invalidated upon resource destruction.
From a technical perspective, use-after-free vulnerabilities exploit race conditions or logical errors in memory management routines. When an object is freed but its pointer remains accessible, subsequent operations may read from or write to that now-invalidated memory region. If the attacker can control what data occupies that freed memory space through heap spraying techniques or other allocation strategies, they can manipulate program behavior arbitrarily. This capability allows for arbitrary code execution with the privileges of the browser process. Given that browsers operate in a sandboxed environment to isolate web content from the host operating system, successfully exploiting this vulnerability would enable an attacker to break out of the browser's security container and execute malicious payloads on the underlying system.
The operational impact of this vulnerability is severe due to its potential for remote code execution via standard web browsing activities. An attacker could craft a specially designed webpage containing malicious JavaScript that triggers the WebGPU use-after-free condition when rendered or interacted with by the victim. Since modern websites increasingly rely on WebGL and emerging standards like WebGPU for complex visualizations, games, and data visualization tools, the attack surface is broad. Successful exploitation leads to full compromise of the user's machine, including theft of sensitive credentials, installation of persistent malware, or use of the system as part of a botnet. The risk is heightened by the fact that many users may not be aware they are interacting with GPU-accelerated content until it is too late.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) identifiers such as CWE-416, which describes use-after-free conditions, and potentially CWE-787 if the memory corruption leads to out-of-bounds writes that facilitate code execution. In terms of threat modeling and adversary tactics, this flaw supports techniques outlined in the MITRE ATT&CK framework under Initial Access via Spearphishing Link or Drive-by Compromise, where malicious web content serves as the delivery mechanism for exploitation. It also relates to Defense Evasion through Obfuscated Files or Information if attackers use complex scripts to hide their intent until execution time.
Mitigation strategies primarily involve applying the vendor-provided software updates that address this specific memory management flaw. Users should ensure they are running Firefox version 155 or later, as well as Firefox Extended Support Release (ESR) version 153.2 or newer. These versions contain patches that likely include rigorous pointer validation checks, improved lifecycle management for GPU resources, and enhanced bounds checking within the WebGPU implementation layer. For organizations managing large fleets of endpoints, automated patching mechanisms should be prioritized to ensure all instances are updated promptly. Additionally, security teams can monitor network traffic for unusual outbound connections following web browsing sessions involving graphics-heavy sites as a heuristic indicator of potential exploitation attempts.