CVE-2026-117911 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Audio/Video: Playback 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 use-after-free conditions within the Audio/Video playback subsystem of Mozilla Firefox browsers. This specific flaw occurs when the application continues to reference a block of memory that has already been deallocated by the system, leading to undefined behavior during media rendering operations. Such vulnerabilities are formally categorized under CWE-416 in the Common Weakness Enumeration standard, which highlights the danger of accessing freed memory regions where the contents may have changed or been reallocated for other purposes. The technical mechanism typically involves a race condition or logic error within the playback engine that fails to properly nullify pointers after releasing associated resources, allowing subsequent operations to interact with stale data structures rather than allocating fresh, secure memory blocks.
The operational impact of this vulnerability is severe because it allows an attacker who can trick a user into visiting a specially crafted webpage containing malicious media content to execute arbitrary code on the victim's system. By carefully crafting the audio or video stream metadata and timing, an adversary can manipulate the heap layout to overwrite critical function pointers or object vtables within the freed memory region. This exploitation path aligns with MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution, as it targets client-side applications through social engineering tactics such as malicious links embedded in emails or websites. Successful exploitation could lead to full system compromise, enabling data exfiltration, installation of persistent malware, or lateral movement within a network if the compromised machine is part of an enterprise environment.
Mitigation strategies primarily rely on applying the vendor-provided patches that address these memory safety issues by enforcing stricter lifecycle management for media objects and ensuring pointers are invalidated immediately after deallocation. Users must update their browsers to Firefox version 159, or the respective Extended Support Release versions 115.44 and 153.6 as soon as possible to eliminate this attack vector. In environments where immediate patching is not feasible, network-level controls such as web filtering proxies can be configured to block access to domains known for hosting malicious media content or those exhibiting patterns consistent with exploit delivery mechanisms. Additionally enabling browser security features like Content Security Policy and disabling unnecessary plugins reduces the surface area available for exploitation while maintaining operational continuity until full remediation is achieved.