CVE-2026-74970 in Firefox
Summary
by MITRE • 08/18/2026
Site isolation issue in the Graphics component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified security flaw resides within the graphics subsystem of Mozilla Firefox, specifically concerning a failure to properly enforce site isolation boundaries. Site isolation is a critical browser security architecture designed to prevent cross-site data leakage by ensuring that resources from different origins are processed in separate processes or memory spaces. When this mechanism fails, it creates an environment where maliciously crafted web content can potentially access sensitive information belonging to other sites loaded within the same browser instance. This vulnerability was addressed and patched in Firefox version 154 as well as the extended support release branch at version 153.1, indicating that users running older versions remain exposed to this specific risk vector until they upgrade their software environment.
From a technical perspective, graphics components often handle complex rendering tasks involving memory allocation for textures, buffers, and display outputs. If the isolation logic governing these resources is flawed, it may allow one site's graphical data structures to be interpreted or accessed by another site's context. This could lead to unauthorized reading of visual content that should remain private, such as images containing sensitive text, canvas elements with proprietary graphics, or even metadata embedded within rendered assets. The flaw likely stems from an improper check during the creation or sharing of graphic resources between different origin contexts, allowing a cross-origin read operation where none was intended by the browser's security model.
The operational impact of this vulnerability is primarily centered on information disclosure and potential privacy violations. An attacker could construct a malicious webpage that exploits this graphics component flaw to exfiltrate visual data from other tabs or windows open in the same Firefox instance. This includes sensitive documents, financial dashboards, personal communications displayed as images, or any content rendered via HTML5 canvas elements. While direct code execution is not explicitly stated as part of this specific site isolation breach, such flaws often serve as stepping stones for more severe attacks by leaking cryptographic keys stored in memory or bypassing same-origin policies that protect user data integrity and confidentiality.
This type of vulnerability aligns with CWE-200, which classifies issues related to the exposure of sensitive information to unauthorized actors, and specifically relates to failures in enforcing isolation boundaries often categorized under cross-site scripting or cross-origin resource sharing misconfigurations depending on the exact mechanism. In terms of adversary tactics, this flaw supports techniques associated with collection phase activities where attackers gather data from compromised browsers without triggering traditional intrusion detection systems that monitor for network exfiltration alone. The lack of proper process separation means that lateral movement within a user's session becomes feasible if an attacker can inject malicious scripts into any tab to probe the graphics subsystem.
To mitigate this risk, organizations and individual users must ensure that Mozilla Firefox is updated to version 154 or later for standard releases, or version 153.1 or later for extended support release channels. Automatic update mechanisms should be verified as active within browser settings to prevent future exposure to similar defects in the graphics stack. Additionally, deploying content security policies and strict same-origin policy enforcement at the application level can provide a secondary layer of defense, although they cannot fully compensate for underlying browser engine vulnerabilities. Security teams should also monitor for any emerging exploits targeting older Firefox versions that have not yet received this patch, particularly in environments where legacy software dependencies prevent immediate upgrades.