CVE-2026-87453 in Chrome
Summary
by MITRE • 09/09/2026
Confused deputy in BackgroundFetch in Google Chrome prior to 153.0.8010.36 allowed a remote attacker who had compromised the renderer process to leak sensitive information 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 a confused deputy flaw within the BackgroundFetch API of Google Chrome prior to version 153.0.8010.36 represents a significant breach in process isolation and privilege management. This issue stems from an improper assignment of permissions, where a component with lower privileges is inadvertently granted access to resources or functions that require higher security clearance. In the context of web browsers, this typically involves the interaction between different execution contexts, specifically between untrusted content loaded by user agents and privileged browser processes responsible for handling network requests and data storage. The BackgroundFetch API allows websites to initiate long-running downloads in the background, a feature designed to improve user experience during poor connectivity or when users navigate away from a page. However, this functionality requires deep integration with the operating system's networking stack and file systems, creating potential attack surfaces if access controls are not strictly enforced between isolated renderer processes and browser services.
The technical flaw arises because an attacker who has successfully compromised a renderer process through other means can exploit the BackgroundFetch API to escalate their privileges or bypass sandbox restrictions. By crafting a specific HTML page that triggers malformed or unexpected calls within the BackgroundFetch implementation, the malicious code leverages the confused deputy scenario. The browser's background service mistakenly treats the request from the compromised renderer as legitimate and authorized, thereby allowing it to access sensitive information such as cookies, local storage data, or other credentials associated with different origins. This misinterpretation of intent allows the attacker to exfiltrate data that should remain isolated within their own origin context, effectively breaking the same-origin policy protections intended to prevent cross-site scripting and data leakage attacks.
The operational impact of this vulnerability is severe for users relying on Chrome for sensitive activities such as online banking or accessing corporate portals. An adversary with renderer process compromise can use this flaw to steal session tokens, authentication cookies, or personally identifiable information stored in web storage. This leads directly to account takeover and identity theft scenarios. From a threat modeling perspective, this aligns closely with CWE-269, which describes Improper Privilege Management, specifically where an actor is granted inappropriate privileges for its current context. Furthermore, the exploitation technique maps to MITRE ATT&CK techniques related to Credential Access via Browser Harvesting or Data from Information Repositories, as well as Defense Evasion through process injection or abuse of legitimate system features like BackgroundFetch to mask malicious activity and avoid detection by endpoint security solutions.
Mitigation for this vulnerability primarily involves updating Google Chrome to version 153.0.8010.36 or later, where the confused deputy issue has been resolved through stricter validation checks within the BackgroundFetch implementation. Developers should ensure that their browser environments are kept up-to-date with the latest security patches provided by vendors. Additionally, organizations can implement content security policies to restrict the use of certain APIs and enforce strict origin isolation for web applications handling sensitive data. Monitoring network traffic for unusual background fetch requests originating from renderer processes may also help in detecting potential exploitation attempts in real-time, although patching remains the most effective defense against this class of privilege escalation flaws.