CVE-2026-117923 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability represents a critical memory management error classified as an out-of-bounds write resulting from use-after-free conditions within the Mozilla Gecko rendering engine's audio and video subsystems. This specific flaw occurs when the application attempts to access or manipulate memory that has already been deallocated by the system, leading to undefined behavior during media playback operations. The root cause typically involves a race condition or improper reference counting where an object is freed while still being referenced by another part of the codebase, particularly in complex asynchronous media processing pipelines. Such errors are notoriously difficult to detect through static analysis alone because they often manifest only under specific timing conditions involving rapid state changes in audio buffers or video frame decoding processes.
From a technical perspective, this vulnerability falls squarely within the Common Weakness Enumeration category CWE-416, which defines use-after-free as a situation where a pointer is used after it has been freed. In the context of web browsers like Firefox, these vulnerabilities are particularly dangerous because they can be triggered by maliciously crafted media files or JavaScript code embedded in websites visited by users. The attacker may exploit this flaw to achieve arbitrary code execution with the privileges of the user running the browser process. By carefully crafting heap layouts and controlling the timing of memory allocations and deallocations, an adversary can overwrite adjacent objects or function pointers within the freed memory region, thereby gaining control over program flow.
The operational impact of such a vulnerability is severe, potentially allowing remote attackers to execute arbitrary code on the victim's machine without any user interaction beyond visiting a malicious webpage containing the exploit payload. This aligns with several techniques in the MITRE ATT&CK framework, specifically T1203 which covers exploitation for client execution and T1059 regarding command and script interpretation if further stages of malware deployment are involved. The browser's sandboxing mechanisms provide some mitigation by limiting the scope of damage to the renderer process, but successful exploitation can still lead to data exfiltration, installation of persistent backdoors, or lateral movement within a network environment depending on how the compromised process interacts with other system resources.
To mitigate this risk, it is imperative that organizations and individual users apply the security patches included in Firefox version 159 as well as the extended support release versions 115.44 and 153.6 immediately upon availability. These updates contain code changes that enforce stricter memory safety checks within the media components, ensuring that pointers are nullified after deallocation or that reference counts are accurately maintained to prevent premature freeing of objects. Additionally, security teams should ensure that browser auto-update features are enabled to minimize exposure windows and consider deploying content security policies that restrict the loading of untrusted multimedia resources from external domains where possible. Regular vulnerability scanning and patch management cycles must be prioritized for all endpoints running affected versions to maintain a robust defense posture against memory corruption exploits targeting modern web browsers.