CVE-2026-87433 in Chrome
Summary
by MITRE • 09/09/2026
Race condition in FileAPI in Google Chrome prior to 153.0.8010.36 allowed a remote attacker who had compromised the renderer process to bypass site isolation 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 CVE-2024-9707 represents a critical race condition within the FileAPI implementation of Google Chrome prior to version 153.0.8010.36. This flaw specifically impacts the browser's ability to maintain strict site isolation boundaries, which are fundamental security mechanisms designed to prevent cross-origin data leakage and mitigate the impact of renderer process compromises. The core technical issue stems from a timing discrepancy in how the FileAPI handles file access requests when interacting with different origins or sandboxed contexts. When an attacker successfully exploits a separate vulnerability within the renderer process to execute arbitrary code, they can leverage this race condition to manipulate the state of file operations before the browser's security checks are fully completed. By carefully crafting HTML pages that trigger these asynchronous file interactions at precise moments, the malicious actor can trick the FileAPI into granting access to resources or metadata associated with a different origin than intended by the site isolation policy.
From an operational perspective, this vulnerability allows for a significant escalation in attack capability beyond standard renderer process compromises. Site isolation is designed to ensure that data from one website cannot be accessed by another, even if both are loaded within the same browser instance. By bypassing these boundaries through the FileAPI race condition, an attacker can potentially exfiltrate sensitive user data such as cookies, local storage contents, or file system artifacts belonging to other sites visited in the same profile. This undermines the principle of least privilege enforced by modern browsers and effectively neutralizes one of Chrome's primary defenses against cross-site scripting attacks that have achieved code execution privileges within a sandboxed renderer. The severity is classified as medium because while it does not allow direct kernel-level exploitation or full system compromise, it significantly weakens the containment strategy for compromised web content.
This vulnerability aligns with CWE-362, which describes concurrent access to shared resources without proper synchronization, leading to race conditions that can be exploited for unauthorized actions. In the context of browser security architecture, this flaw also relates to CWE-1058, involving improper enforcement of a behavioral constraint during resource initialization or modification. The attack vector is categorized under MITRE ATT&CK technique T1210, which covers exploitation of remote services through application software vulnerabilities, specifically leveraging client-side execution environments like web browsers. Furthermore, the bypass of site isolation mechanisms falls under the broader category of privilege escalation within a sandboxed environment, often associated with techniques that aim to break out of restricted contexts to access higher-privilege data stores.
Mitigation for this vulnerability requires immediate updates to Google Chrome and its underlying Chromium engine components to version 153.0.8010.36 or later, where the race condition in the FileAPI has been resolved through improved synchronization mechanisms during file operation handling. Organizations should enforce automated update policies to ensure all client machines are patched against this specific flaw. Additionally, security teams should monitor for indicators of compromise that suggest exploitation attempts involving crafted HTML files designed to trigger asynchronous file access patterns from renderer processes. Implementing strict content security policies and disabling unnecessary browser features can further reduce the attack surface, although patching remains the primary defense against this type of logic-based vulnerability in web rendering engines.