CVE-2026-95301 in Chrome
Summary
by MITRE • 09/29/2026
Missing authorization in Extensions in Google Chrome prior to 154.0.8037.57 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted HTML page. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability identified as missing authorization within the Extensions subsystem of Google Chrome prior to version 154.0.8037.57 represents a critical failure in access control mechanisms that governs how browser extensions interact with the underlying rendering engine and site isolation policies. Site isolation is a fundamental security architecture designed to prevent cross-site data theft by ensuring that processes handling content from different origins are strictly separated, thereby mitigating attacks such as Spectre or simple side-channel information leaks. When this mechanism relies on robust authorization checks within extension APIs, any lapse allows malicious code executed via an extension context to bypass these boundaries. In this specific instance, the flaw stems from a logic error where the browser fails to verify whether the requesting entity possesses the necessary permissions to access resources across origin boundaries when operating through the extensions interface.
A remote attacker who has successfully compromised the renderer process of a victim's browser can exploit this deficiency by crafting a malicious HTML page that leverages specific extension APIs or injection vectors. By triggering these crafted requests, the attacker forces the browser to execute actions under the context of an extension with elevated privileges rather than the restricted permissions of the web content itself. This effectively neutralizes the protective barriers established by site isolation, allowing the compromised renderer process to read sensitive data from other tabs or sites that it should not be able to access. The severity is classified as high because this bypass undermines one of Chrome's most effective defenses against cross-site scripting and data exfiltration attacks, potentially leading to unauthorized access to cookies, local storage, session tokens, and other confidential user information stored across different domains.
The operational impact of this vulnerability extends beyond immediate data theft, as it erodes the trust model that users place in their web browsers. If an attacker can bypass site isolation through extension mechanisms, they gain a persistent foothold within the browser environment that is difficult to detect using standard security monitoring tools. This capability enables sophisticated phishing campaigns where sensitive credentials are harvested without triggering typical warning indicators associated with cross-origin requests. Furthermore, because extensions often have broad permissions by design, exploiting this authorization gap allows an attacker to escalate privileges from a low-level renderer process to one capable of interacting with the browser's core functionality and other user data stores. This aligns closely with CWE-269, which describes Improper Privilege Management, specifically where access control checks are omitted or incorrectly implemented for specific system resources.
To mitigate this risk, users must ensure that Google Chrome is updated to version 154.0.8037.57 or later, as the vendor has patched the authorization logic within the extensions subsystem. Administrators should enforce automatic update policies across all endpoints to prevent exposure during the window between vulnerability disclosure and patch deployment. Additionally, security teams should audit installed browser extensions for unnecessary permissions, adhering to the principle of least privilege by removing any extension that requests broad access rights without a clear functional necessity. Monitoring network traffic for anomalous cross-origin resource sharing patterns or unexpected API calls from renderer processes can also aid in detecting exploitation attempts before significant data loss occurs. This incident underscores the importance of rigorous code review practices within browser extensions and highlights the ATT&CK technique T1059, Command and Scripting Interpreter, where attackers use system utilities to execute malicious commands that bypass security boundaries through legitimate application features.