CVE-2026-87436 in Chrome
Summary
by MITRE • 09/09/2026
Incomplete cleanup in Browser in Google Chrome prior to 153.0.8010.36 allowed a remote attacker leveraging social engineering to bypass web origin policy via a crafted Chrome extension. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an incomplete cleanup issue within the browser component of Google Chrome prior to version 153.0.8010.36 represents a significant deviation from expected state management protocols during the lifecycle of web extensions. This flaw is categorized under CWE-479, which describes a missing or incorrect return value in a subroutine that fails to properly clean up resources or reset internal states after an operation completes. In the context of modern browser architecture, extensions operate within specific security boundaries designed to isolate them from other web content and restrict their access to sensitive APIs unless explicitly granted by the user. The incomplete cleanup mechanism implies that when certain extension-related processes are terminated or unloaded, residual data structures, permissions, or contextual states remain active in memory rather than being fully revoked or reset. This creates a window of opportunity where the browser's internal state does not accurately reflect the actual permission level assigned to the extension, effectively leaving security controls partially engaged but functionally bypassed.
The operational impact of this vulnerability is primarily centered on the potential for unauthorized access to web origins and sensitive user data through social engineering tactics. An attacker leveraging this flaw would typically craft a malicious Chrome extension that appears legitimate or benign to the end-user during installation. Once installed, the extension might request standard permissions such as reading browsing history or accessing specific websites. However, due to the incomplete cleanup logic, if the extension attempts to revoke these permissions or is removed by the user while certain background processes are still active, the browser may fail to properly sever the connection between the extension and its previously granted privileges. This allows a remote attacker to maintain access to resources that should have been restricted, thereby bypassing web origin policies. The reliance on social engineering indicates that the initial vector requires user interaction, such as installing the malicious add-on or enabling specific features within it, which aligns with ATT&CK technique T1176 (Browser Extensions) and potentially T1059 (Command and Scripting Interpreter) if the extension executes further scripts to exfiltrate data.
From a technical perspective, this vulnerability highlights critical challenges in managing asynchronous operations and state transitions within complex software ecosystems like web browsers. When an extension is uninstalled or disabled, the browser must ensure that all associated event listeners are removed, memory allocations are freed, and permission grants are revoked at the policy engine level. The failure to perform these steps completely suggests a race condition or a logic error in the cleanup routine where certain code paths do not trigger the necessary de-initialization functions. This can lead to scenarios where an extension retains access to cookies, local storage, or DOM elements of websites it is no longer authorized to interact with. Such persistence violates the principle of least privilege and undermines the integrity of the browser's sandboxing mechanisms, which are fundamental to preventing cross-site scripting attacks and data leakage between different web origins.
Mitigation strategies for this vulnerability involve immediate updates to the affected software version. Users running Google Chrome prior to 153.0.8010.36 should update their browsers immediately as patches have been released by Chromium developers to address these state management flaws. Beyond patching, security administrators and individual users are advised to exercise caution when installing third-party extensions from untrusted sources or those with excessive permission requests. Regular auditing of installed extensions can help identify any suspicious add-ons that may be exploiting this flaw before an update is applied. Additionally, enabling strict content security policies within the browser settings where possible can provide an additional layer of defense by limiting the capabilities available to web applications and extensions. Organizations should also consider implementing application whitelisting solutions to prevent unauthorized software execution, thereby reducing the attack surface presented by social engineering campaigns targeting extension installations.