CVE-2026-87603 in Chrome
Summary
by MITRE • 09/09/2026
Missing authorization in FileSystem in Google Chrome prior to 153.0.8010.36 allowed a remote attacker to bypass system access restrictions via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as missing authorization within the file system handling mechanisms of Google Chrome represents a significant lapse in access control logic, specifically affecting versions prior to 153.0.8010.36. This flaw stems from an insufficient validation process where the browser fails to properly verify whether a web page or script has legitimate permission to interact with specific local file system resources. In modern web browsers, sandboxing is employed to isolate untrusted content from the host operating system, but this isolation relies heavily on strict enforcement of authorization checks when APIs that interface with local storage are invoked. When these checks are bypassed due to a coding error or logical oversight in the Chromium engine, it creates an avenue for unauthorized data access and potential manipulation of local files by malicious actors.
From a technical perspective, this vulnerability is classified under CWE-269, which denotes Improper Privilege Management, specifically focusing on context-dependent authorization failures. The core issue lies in the failure to enforce security boundaries when processing requests that involve file system operations such as reading, writing, or deleting files via HTML5 APIs like the File System Access API or legacy methods involving local storage interactions. A remote attacker can exploit this by crafting a malicious HTML page containing JavaScript code designed to trigger these specific file system functions without proper user consent or permission verification. Because the browser does not correctly validate the origin and intent of the request against the current security context, it grants access that should have been denied, effectively breaking the sandbox model intended to protect the end-user's data integrity.
The operational impact of this vulnerability is substantial for users who rely on Chrome as their primary web browsing tool while handling sensitive local files or working in environments where file system integrity is critical. An attacker leveraging a crafted HTML page can potentially read confidential documents, exfiltrate personal information stored locally, or even modify existing files to introduce malware or corrupt data structures. This capability undermines the trust users place in browser-based applications and poses risks not only to individual privacy but also to organizational security postures where local file systems may contain proprietary code, financial records, or other regulated data. The medium severity rating assigned by Chromium reflects that while exploitation requires user interaction such as visiting a malicious site, the consequences of successful exploitation are severe enough to warrant immediate attention and patching.
To mitigate this risk, organizations and individual users must ensure that Google Chrome is updated to version 153.0.8010.36 or later, where these authorization checks have been reinforced. Beyond software updates, implementing strict Content Security Policies can help restrict the execution of scripts from untrusted origins, thereby reducing the attack surface available to remote attackers. Additionally, users should be educated on the risks associated with visiting unknown websites and enabling browser features that prompt for explicit permissions before allowing access to sensitive system resources. Monitoring network traffic for unusual file system API calls during web sessions can also aid in detecting potential exploitation attempts in real-time. This incident underscores the importance of rigorous code review processes focused on security-critical paths involving operating system interactions, ensuring that privilege escalation vectors are systematically eliminated through robust implementation of standard authorization frameworks aligned with industry best practices such as those outlined in OWASP guidelines for client-side protection.