CVE-2026-87570 in Chrome
Summary
by MITRE • 09/09/2026
Incorrect authorization in SiteIsolation in Google Chrome prior to 153.0.8010.36 allowed a remote attacker who had compromised the renderer process and leveraged social engineering to bypass site isolation via a crafted file. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an incorrect authorization flaw within Google Chrome's SiteIsolation mechanism prior to version 153.0.8010.36 represents a significant breach in the browser's process isolation architecture. SiteIsolation is a critical security feature designed to prevent cross-site scripting and data theft by ensuring that each site runs in its own unique renderer process, thereby isolating sensitive data from potentially malicious content loaded from other origins. The flaw arises when the authorization checks governing access between these isolated processes are not strictly enforced or contain logical errors that allow unauthorized communication paths to be established. This specific weakness enables a remote attacker who has already achieved code execution within a compromised renderer process to escalate their privileges and break out of the sandboxed environment, effectively bypassing the site isolation boundaries intended to protect user data across different websites.
The operational impact of this vulnerability is severe because it undermines one of Chrome's primary defenses against cross-site attacks. By leveraging social engineering techniques such as phishing or malicious file downloads, an attacker can trick a victim into interacting with crafted content that triggers the authorization bypass. Once inside a renderer process through initial compromise, the attacker exploits the flawed logic to communicate with processes belonging to other sites or even higher-privilege browser components. This allows for potential data exfiltration from unrelated tabs, session hijacking, and further lateral movement within the user's browsing context. The severity is classified as medium by Chromium security standards because while it requires an initial foothold via social engineering, the ability to bypass site isolation significantly expands the attack surface and reduces the effectiveness of existing sandbox protections.
From a classification perspective, this vulnerability aligns with CWE-269 Improper Privilege Management and CWE-862 Missing Authorization, as the core issue lies in the failure to properly restrict access rights between isolated processes. In terms of offensive security frameworks, it maps to MITRE ATT&CK techniques related to Process Injection or Defense Evasion, specifically where an attacker leverages legitimate system mechanisms like browser process isolation for malicious purposes after initial compromise. The exploitation path typically involves crafting a file that, when opened within the Chrome environment, triggers the specific code paths responsible for inter-process communication checks, allowing the renderer to send commands or data to unauthorized targets without proper validation of its origin and permissions.
Mitigation strategies primarily involve updating Google Chrome to version 153.0.8010.36 or later, where these authorization logic errors have been corrected by developers through rigorous code review and testing. Organizations should enforce automatic update policies for all endpoints running the browser to ensure timely patching of such vulnerabilities. Additionally, users must remain vigilant against social engineering tactics that lead to opening untrusted files within browsers, as this is often the initial vector required to trigger such complex exploitation chains. Security teams should also monitor for anomalous inter-process communication patterns in endpoint detection and response systems, although direct visibility into browser internals remains limited without specialized tools. Regular security awareness training regarding file handling practices complements technical controls by reducing the likelihood of successful social engineering attacks that precede this type of exploit.