CVE-2026-78976 in Chrome
Summary
by MITRE • 08/26/2026
Improper input validation in StorageAccessAPI in Google Chrome prior to 152.0.7977.65 allowed a remote attacker who had compromised the renderer process to bypass web origin policy via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability identified as an improper input validation flaw within the StorageAccessAPI of Google Chrome prior to version 152.0.7977.65 represents a significant breach in browser isolation mechanisms. This specific component is responsible for managing cross-site storage access permissions, which are critical for maintaining the separation between different web origins while allowing legitimate data sharing under controlled conditions. The core technical flaw lies in the insufficient sanitization and validation of inputs processed by this API when handling requests from compromised renderer processes. In modern browser architectures, such as Chromium's multi-process model, each tab or frame typically runs in a separate sandboxed process known as the renderer. These renderers are strictly isolated to prevent malicious code executed within one context from accessing sensitive data or performing actions on behalf of another origin without explicit permission. However, when an attacker successfully compromises a renderer process through other means, such as exploiting a different vulnerability like a use-after-free or buffer overflow, they gain execution capabilities within that sandboxed environment. The flaw in the StorageAccessAPI allows this compromised renderer to craft specific HTML pages and API calls that exploit the validation gap, effectively tricking the browser into granting elevated storage access privileges across origins where they should not be permitted.
This bypass of web origin policies has severe operational implications for user security and privacy. Web origin policy is a fundamental security concept enforced by browsers to prevent malicious websites from accessing data belonging to other sites, such as cookies, local storage contents, or session tokens. By circumventing this restriction through the StorageAccessAPI flaw, an attacker can potentially exfiltrate sensitive user information stored in cross-site contexts. This could include personal identifiable information, financial details, authentication credentials, or behavioral tracking data that users assume is isolated from other domains they visit. The ability to bypass these policies undermines the trust model of the web ecosystem, as it allows a compromised page on one domain to read and potentially modify stateful data associated with another trusted domain. This type of attack vector is particularly dangerous because it leverages legitimate browser functionality for malicious purposes, making detection by traditional security tools more difficult compared to direct exploitation attempts that trigger obvious error states or crashes.
From a classification perspective, this vulnerability aligns closely with CWE-20 Improper Input Validation and CWE-913 Control of Resource Through Uncontrolled Frequency. The failure to adequately validate inputs from the renderer process before granting storage access permissions constitutes a classic input validation weakness. Furthermore, because the attack relies on manipulating the browser's internal state management regarding cross-origin resource sharing, it relates to issues surrounding improper enforcement of security policies for shared resources. In terms of offensive cyber operations and threat modeling, this vulnerability maps directly to MITRE ATT&CK technique T1059 Command and Scripting Interpreter if viewed through the lens of executing scripts within the browser context, but more accurately fits into T1213 Data from Information Repositories or potentially T1537 Transfer Data to Cloud Account via Unencrypted Non-Ceased Channel depending on how the exfiltrated data is handled. The specific mechanism of bypassing origin policies places it firmly in the category of privilege escalation within the application layer, allowing a lower-privilege context (compromised renderer) to achieve higher-level access (cross-origin storage).
Mitigation for this vulnerability primarily involves updating Google Chrome to version 152.0.7977.65 or later, where these input validation checks have been hardened and the logic governing StorageAccessAPI permissions has been corrected to prevent unauthorized cross-origin data retrieval. For organizations deploying browsers at scale, ensuring automatic update policies are enforced is critical to closing this window of exposure. Additionally, security teams should monitor for indicators of compromise that suggest renderer process exploitation attempts, such as unusual network traffic patterns originating from browser processes or unexpected access logs in web applications indicating potential session hijacking via stolen storage tokens. Implementing strict Content Security Policy headers can also provide a layer of defense-in-depth by restricting the sources from which scripts and resources are loaded, thereby reducing the attack surface available to an attacker who has already gained entry into a renderer process. Regular security audits focusing on browser extension permissions and third-party script integrations further reduce the likelihood of initial compromise that leads to exploitation of this specific API flaw.