CVE-2026-87471 in Chrome
Summary
by MITRE • 09/09/2026
Incorrect authorization in ServiceWorker 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 an incorrect authorization flaw within the ServiceWorker component of Google Chrome prior to version 153.0.8010.36 represents a significant breach in the browser's multi-process architecture, specifically targeting the site isolation mechanism. Site isolation is a critical security feature designed to prevent cross-site data theft by ensuring that each website runs in its own unique process with separate memory spaces. This architectural separation prevents malicious scripts from one origin from accessing sensitive data belonging to another origin, even if they are rendered on the same page or share similar DOM structures. The flaw arises because the authorization checks governing ServiceWorker operations were insufficiently rigorous, allowing a compromised renderer process to execute actions that should have been restricted by its originating context.
From a technical perspective, this vulnerability falls under CWE-269, which denotes Improper Control of Interaction with Untrusted Input, specifically manifesting as an elevation of privilege within the browser's internal logic. When a renderer process is compromised through typical web-based attack vectors such as cross-site scripting or drive-by downloads, it operates under strict sandbox constraints intended to limit its impact on the rest of the system and other tabs. However, due to this authorization error, an attacker leveraging a crafted HTML page could trick the ServiceWorker into performing operations that bypass these isolation boundaries. This effectively allows the malicious code to communicate with origins it should not have access to, undermining the fundamental security model that Chrome relies upon to protect user privacy and data integrity against cross-site attacks.
The operational impact of this vulnerability is severe because it neutralizes one of the most effective defenses against sophisticated web-based espionage and data exfiltration campaigns. By bypassing site isolation, an attacker can potentially access cookies, local storage, IndexedDB entries, or other sensitive artifacts associated with high-value targets such as banking portals, email services, or corporate intranets. This capability aligns closely with the MITRE ATT&CK technique T1530, Data from Local System, and more specifically T1048, Exfiltration Over Alternative Protocol, as it facilitates the unauthorized retrieval of data across security boundaries. The severity is classified as Medium by Chromium because while it requires a pre-existing compromise of the renderer process to exploit, the resulting breach in isolation significantly amplifies the potential damage of that initial foothold, enabling lateral movement within the user's browsing session and increasing the risk of account takeover or sensitive information leakage.
Mitigation for this vulnerability primarily involves updating Google Chrome to version 153.0.8010.36 or later, where these authorization checks have been corrected to enforce stricter boundaries between ServiceWorker contexts and their originating sites. In environments where immediate patching is not feasible, administrators should consider implementing strict Content Security Policy directives that limit the execution of untrusted scripts and restrict service worker registration scopes to known trusted origins only. Additionally, enabling advanced browser security features such as Enhanced Protection in Chrome's Safe Browsing settings can provide an additional layer of defense by blocking access to dangerous sites before they have the opportunity to exploit renderer vulnerabilities. Regular auditing of installed extensions is also recommended, as malicious extensions often serve as a vector for compromising the renderer process and initiating this type of isolation bypass attack.