CVE-2026-92005 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 156, Firefox ESR 140.16, and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/16/2026
The identified vulnerability represents a critical memory management error within the Mozilla Firefox browser's Audio/Video Web Codecs component, specifically classified as an use-after-free condition. This type of flaw occurs when software continues to reference a pointer after the memory it points to has been deallocated or freed by the system. In the context of web technologies, this often involves complex interactions between JavaScript engines and native C++ code handling media streams. When a webpage utilizes Web APIs to decode audio or video data, the underlying engine allocates specific buffers for processing these multimedia frames. If the application logic fails to properly synchronize object lifecycles with memory deallocation events, it may retain references to memory regions that have already been returned to the heap allocator. Subsequent operations attempting to access this stale pointer result in undefined behavior, as the memory might now contain unrelated data or be completely unmapped by the operating system.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow an attacker to manipulate how the browser interprets arbitrary memory contents. By carefully crafting malicious web content that triggers the premature freeing of media codec resources while maintaining active references within JavaScript objects, an adversary can control what data is read from or written to these freed regions. This capability effectively breaks the isolation boundaries between different tabs and processes in Firefox's multi-process architecture. The vulnerability exploits race conditions or logical errors in reference counting mechanisms where the final release of a codec object does not immediately nullify all existing pointers held by other components, such as the media pipeline or JavaScript bindings.
The operational impact of this flaw is severe, potentially leading to arbitrary code execution with the privileges of the user running the browser. An attacker could design a specially crafted website that, when visited by a victim, triggers the use-after-free condition in real-time. Through sophisticated exploitation techniques such as heap spraying or controlled overwrites, malicious actors can redirect program flow to execute their own shellcode. This compromises the confidentiality and integrity of the user's system, allowing for data theft, installation of malware, or further lateral movement within a network if the browser is used on corporate devices. The risk is amplified by the ubiquity of web-based media playback in modern applications, making this vector highly attractive to threat actors seeking remote code execution capabilities without requiring user interaction beyond visiting a malicious page.
Industry standards categorize this flaw under CWE-416, which defines use-after-free as an error where software uses memory after it has been freed. This classification highlights the fundamental failure in resource management that characterizes such vulnerabilities. Furthermore, from a tactical standpoint aligned with MITRE ATT&CK frameworks, exploitation of this vulnerability falls under techniques related to initial access and execution via browser-based attacks. Attackers frequently leverage these types of zero-day or recently patched flaws within web browsers as part of drive-by download campaigns or targeted spear-phishing efforts where the primary goal is establishing a foothold on an endpoint through trusted software vulnerabilities rather than direct application exploits.
Mitigation strategies primarily involve applying the vendor-provided patches immediately upon availability, which in this case corresponds to updating Firefox to version 156 and ensuring that Extended Support Release (ESR) users are updated to versions 140.16 or 153.3 respectively. These updates contain code changes that enforce stricter memory management protocols within the Web Codecs implementation, likely involving improved reference counting logic, explicit nullification of pointers after deallocation, and enhanced bounds checking during media processing operations. For organizations unable to patch immediately due to compatibility concerns, network-level controls such as web filtering proxies can be configured to block access to known malicious domains or restrict execution of untrusted JavaScript that interacts heavily with multimedia APIs. Additionally, enabling strict content security policies and disabling unnecessary browser features like autoplay for unknown sources can reduce the attack surface available to exploit this specific memory corruption flaw until a permanent fix is deployed across all endpoints.