CVE-2026-74967 in Firefox
Summary
by MITRE • 08/18/2026
Same-origin policy bypass in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified vulnerability represents a critical breach of the Same-Origin Policy within Mozilla Firefox's Audio/Video playback subsystem. The Same-origin policy is a fundamental security mechanism in web browsers that restricts how a document or script loaded from one origin can interact with resources from another origin. This isolation prevents malicious websites from accessing sensitive data, such as cookies, local storage, or DOM elements, belonging to other sites without explicit permission. In this specific instance, the flaw resides in the handling of media playback contexts, where improper boundary checks allow a webpage hosted on an untrusted domain to access or manipulate resources associated with a different origin during audio or video rendering operations.
Technically, the vulnerability likely stems from insufficient validation when establishing cross-origin references for media elements. When browsers process multimedia content, they often create internal objects and context stacks that manage playback state, buffering, and event handling. If these internal structures fail to correctly enforce isolation boundaries between different origins, a malicious actor can exploit this gap. By crafting specific HTML5 video or audio tags with carefully manipulated attributes or JavaScript interactions, an attacker could trick the browser into exposing data from a victim's session on a trusted site. This bypass allows for potential information disclosure, where sensitive content displayed within media players or metadata associated with them becomes accessible to scripts running in a malicious context.
The operational impact of this vulnerability is significant because it undermines one of the core pillars of web security. An attacker could potentially exfiltrate private user data by reading properties from cross-origin media elements that should remain isolated. This might include accessing video frames, audio buffers, or associated metadata that contain sensitive information. Furthermore, if the playback context shares state with other browser components, it could facilitate more complex attacks such as clickjacking or session hijacking scenarios where the attacker gains insight into user behavior or authentication states tied to media consumption on trusted platforms. The risk is particularly acute for users who frequently access banking, healthcare, or corporate portals while consuming multimedia content from untrusted sources.
This issue has been addressed in Firefox version 154 as well as extended support releases including ESR versions 140.14 and 153.1. These updates implement stricter checks within the media playback engine to ensure that cross-origin restrictions are correctly applied during all stages of audio and video processing. Users should upgrade their browsers immediately to mitigate this risk, ensuring that the latest security patches are active. Additionally, developers relying on Firefox for testing or deployment environments must verify compatibility with these updated versions to maintain secure interactions between web applications and media resources.
From a classification perspective, this vulnerability aligns with CWE-200, which covers exposure of sensitive information to an unauthorized actor, specifically through improper access control mechanisms in browser engines. It also relates to the concept of cross-origin resource sharing failures often categorized under broader injection or bypass vulnerabilities found in web application frameworks. In terms of MITRE ATT&CK mapping, this flaw could be leveraged within techniques related to Collection via Screen Capture or Data from Information Repositories if an attacker successfully exploits it to gather sensitive visual or auditory data without user consent. Maintaining up-to-date software is the primary defense against such browser-level exploitation vectors that target foundational web standards enforcement mechanisms.