CVE-2026-74968 in Firefox
Summary
by MITRE • 08/18/2026
Site isolation issue in the Graphics: WebRender 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 WebRender graphics subsystem of Mozilla Firefox, specifically concerning a site isolation breach that undermines the browser's ability to maintain strict boundaries between different web origins. Site isolation is a critical defense mechanism designed to prevent cross-site information leakage by ensuring that resources from one origin cannot access data or state associated with another origin, even if they are loaded within the same process. In this instance, the vulnerability allows an attacker-controlled webpage to potentially bypass these isolation guarantees through specific interactions with the WebRender component, which is responsible for rendering web content using GPU-accelerated compositing and drawing operations. The flaw likely stems from improper handling of resource ownership or context switching during complex graphical operations, enabling a malicious site to infer sensitive information about other open tabs or windows that share the same browser process but belong to different origins.
From a technical perspective, this vulnerability represents a failure in enforcing strict origin separation at the graphics layer, which can lead to side-channel attacks such as cache timing attacks or memory disclosure if the renderer fails to properly clear or isolate graphical buffers between contexts. Such flaws are particularly dangerous because they operate beneath the standard same-origin policy enforced by JavaScript engines and network stacks, making them difficult for traditional web security models to detect. The impact of this vulnerability is significant in environments where users frequently interact with untrusted content alongside sensitive applications like online banking portals or email clients. An attacker could exploit this weakness to exfiltrate data such as cookies, session tokens, or user interface states from a victim's other browsing sessions by analyzing rendering artifacts or timing differences caused by the shared graphical resources.
This issue aligns closely with CWE-200, which classifies information exposure vulnerabilities where sensitive system information is available to unauthorized actors without explicit intent. Furthermore, it relates to ATT&CK technique T1537, Transfer Data to Cloud Account via Exfiltrated Information, as the ultimate goal of such a breach would be to transmit stolen data from the victim's browser context to an external server controlled by the attacker. The vulnerability highlights the complexity of maintaining security in modern browsers where multiple layers of isolation must work in concert across CPU and GPU resources. Without proper site isolation at the graphics level, the entire trust model of the browser is compromised, allowing for sophisticated cross-site tracking or data theft that bypasses conventional sandboxing measures.
To mitigate this risk, users are strongly advised to upgrade immediately to Firefox version 154 or Firefox Extended Support Release (ESR) version 153.1, where these site isolation boundaries have been reinforced and the WebRender component has been patched to prevent unauthorized cross-origin access. Organizations should ensure that their deployment pipelines enforce automatic updates for all installed instances of Firefox to minimize exposure windows. Additionally, security teams can monitor browser telemetry or network logs for unusual patterns indicative of side-channel exploitation attempts, although such detection is challenging due to the low-volume nature of these attacks. Implementing strict content security policies and disabling unnecessary plugins or extensions that interact heavily with graphics rendering can further reduce the attack surface while waiting for full patch deployment across all endpoints.