CVE-2026-117903 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.
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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 resulting from a use-after-free condition within the Audio/Video subsystem of Mozilla Firefox browsers. 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 and potential code execution under controlled conditions. The vulnerability was addressed in recent security updates for Firefox version 159 as well as extended support releases including ESR versions 115.44 and 153.6, indicating a significant effort to remediate this high-risk issue across both standard and enterprise deployment environments.
From a technical perspective, use-after-free vulnerabilities arise when pointers continue to reference memory blocks after they have been freed without being properly nullified or reallocated. In the context of multimedia processing components like Audio/Video handling in Firefox, complex state management is required to manage streams, codecs, and rendering pipelines. If an object representing media data is destroyed while still referenced by another part of the application logic, subsequent operations on that dangling pointer can lead to arbitrary memory writes. This capability allows attackers to overwrite adjacent heap metadata or function pointers, which serves as a primary mechanism for achieving remote code execution when combined with other exploitation techniques such as heap spraying or type confusion attacks.
The operational impact of this vulnerability is severe due to its potential for remote code execution through maliciously crafted web content. An attacker could host a specially designed webpage containing exploit code that triggers the use-after-free condition within the browser's media processing engine. Upon visiting this page, the victim’s browser would execute arbitrary commands with the privileges of the user account running the application. This scenario aligns closely with ATT&CK technique T1203 Exploitation for Client Execution and CWE-416 Use After Free, highlighting the direct path from web-based interaction to system compromise without requiring additional social engineering or local access prerequisites beyond initial browsing activity.
Mitigation strategies primarily involve ensuring that all client systems are updated to include the patched versions of Firefox mentioned above. For enterprise environments utilizing Extended Support Releases such as ESR 115 and ESR 153, administrators must verify that automatic update policies are correctly configured to deploy version 115.44 or 153.6 respectively. Additionally, organizations should consider implementing browser isolation technologies or content security policies that restrict the execution of untrusted scripts within media contexts where possible. Regular vulnerability scanning and patch management cycles remain essential defenses against such memory corruption flaws which are frequently targeted by advanced persistent threats seeking initial access vectors through widely used software components.