CVE-2026-78954 in Chrome
Summary
by MITRE • 08/26/2026
Incorrect authorization in Extensions 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: High)
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability identified as an incorrect authorization flaw within Google Chrome's extension system prior to version 152.0.7977.65 represents a significant breach in the browser's isolation mechanisms, specifically targeting the boundary between renderer processes and privileged extension contexts. This issue stems from a failure in enforcing strict access controls when extensions interact with web content or internal browser APIs. In modern browsers like Chrome, security relies heavily on the principle of least privilege and process isolation to prevent malicious code executed within untrusted environments from accessing sensitive data or performing unauthorized actions. The renderer process is designed to be sandboxed, meaning it should not have direct access to user credentials, cookies, or other protected resources without explicit permission through well-defined interfaces. However, this flaw allowed a remote attacker who had already achieved code execution within the renderer process via a crafted HTML page to bypass these web origin policies effectively neutralizing one of the primary defenses against cross-site scripting and data exfiltration attacks.
From a technical perspective, the core issue lies in how extensions are authorized to perform actions that typically require higher privileges than standard web pages possess. Extensions often operate with elevated permissions granted by the user during installation, such as access to browsing history or the ability to modify page content. The vulnerability exploited a gap where these extended capabilities were not correctly validated against the origin of the calling context within certain extension APIs. By crafting an HTML page that leveraged specific JavaScript interfaces exposed by extensions, an attacker could trick the browser into treating malicious script from any domain as if it originated from a trusted source or possessed higher-level permissions than intended. This bypass allows for unauthorized data access and manipulation, undermining the integrity of the browsing session. The severity is classified as high because successful exploitation can lead to severe privacy violations and potential account takeover scenarios depending on the specific extensions installed by the victim.
The operational impact of this vulnerability is substantial, particularly in enterprise environments or among users who rely heavily on third-party browser extensions for productivity and security tools. An attacker leveraging this flaw could potentially steal sensitive information such as session cookies, authentication tokens, or personal data stored within web applications that assume they are protected by the same-origin policy. Furthermore, because the attack vector involves a remote HTML page, it can be delivered through phishing campaigns, malicious advertisements, or compromised websites without requiring any user interaction beyond visiting the site if drive-by download techniques were also present in conjunction with other vulnerabilities. This makes it a potent tool for large-scale data theft and surveillance operations targeting high-value individuals or organizations.
To mitigate this risk, users must immediately update Google Chrome to version 152.0.7977.65 or later where these authorization checks have been hardened. It is also advisable to review installed extensions regularly and remove any that are no longer needed or appear suspicious, as reducing the attack surface minimizes the potential for exploitation through extension-related flaws. Security teams should monitor browser telemetry for unusual activity patterns indicative of origin policy bypasses and ensure that endpoint detection systems are configured to flag anomalous network requests originating from renderer processes attempting to access restricted resources. Adhering to industry standards such as CWE-269 which addresses improper authorization, and recognizing the attack pattern within MITRE ATT&CK framework under techniques related to privilege escalation or defense evasion through browser exploitation is critical for maintaining robust security postures against evolving web-based threats.