CVE-2026-121135 in Chrome
Summary
by MITRE • 11/03/2026
Security issue in Platform in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to bypass web origin policy via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in Google Chrome versions prior to 157.0.8103.38 represents a significant breach of the browser's core security model, specifically targeting the Web Origin Policy mechanism. This policy is fundamental to web security as it restricts how documents or scripts loaded from one origin can interact with resources from another origin. By allowing a remote attacker to bypass this restriction through a crafted HTML page, the vulnerability undermines the isolation between different websites and applications running within the browser environment. The Chromium project has classified this issue with a medium severity rating, indicating that while it may not lead directly to full system compromise in all scenarios, it poses a substantial risk to data confidentiality and integrity by enabling unauthorized cross-origin access.
At its technical core, this flaw involves a failure in the enforcement of same-origin policies within the rendering engine or associated security checks. When an attacker hosts a malicious HTML page designed to exploit specific conditions in Chrome's handling of web resources, they can trick the browser into treating content from their domain as if it originated from a trusted target site. This bypass typically occurs when the browser incorrectly validates origin headers, fails to properly sanitize input that influences navigation or resource loading, or misinterprets security boundaries during complex interactions between frames and scripts. The crafted page likely leverages specific features of modern web standards such as Cross-Origin Resource Sharing (CORS) mechanisms, iframe sandboxing attributes, or history API manipulations to achieve this unauthorized access without triggering standard browser warnings or blocks.
The operational impact of this vulnerability is primarily centered on data theft and session hijacking scenarios. An attacker who successfully exploits this flaw can read sensitive information from other websites that the victim has visited and remains authenticated against. This includes personal identifiable information, financial details, private communications, or proprietary business data stored in local storage or accessible via AJAX requests. Furthermore, if the targeted site supports state-changing operations like fund transfers or account modifications, the attacker could potentially perform actions on behalf of the user without their knowledge or consent. This erosion of trust in web applications can lead to severe financial loss and reputational damage for both individual users and organizations relying on secure browser-based interactions.
From a classification perspective, this vulnerability aligns with CWE-284 Improper Access Control, as it involves an attacker gaining access to resources they are not authorized to view or modify. It also maps closely to MITRE ATT&CK techniques related to Cross-Site Scripting and Data from Browser Memory, specifically the ability to exfiltrate data by bypassing isolation boundaries. Understanding these mappings helps security teams contextualize the risk within broader threat landscapes where attackers seek to leverage browser weaknesses for initial access or lateral movement in enterprise environments.
To mitigate this vulnerability, organizations must ensure that all instances of Google Chrome are updated to version 157.0.8103.38 or later immediately upon availability. For users unable to update instantly due to compatibility concerns with internal applications, implementing strict Content Security Policy headers on web properties can help restrict the types of scripts and resources allowed to execute, thereby reducing the attack surface even if the browser itself is vulnerable. Additionally, deploying advanced threat protection solutions that monitor for anomalous cross-origin requests or unusual script execution patterns can provide an additional layer of defense against exploitation attempts. Regular security audits focusing on origin validation logic in web applications are also recommended to ensure resilience against similar bypass techniques in future updates.