CVE-2026-121107 in Chrome
Summary
by MITRE • 11/03/2026
Incorrect authorization in BackgroundFetch 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: High)
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified as an incorrect authorization flaw within the Background Fetch API of Google Chrome, specifically affecting versions prior to 157.0.8103.38, represents a significant breach in web origin policy enforcement. This component is designed to allow websites to perform long-running background tasks that continue even after the user has navigated away from or closed the page hosting them. The core technical flaw lies in the improper validation of authorization contexts during these asynchronous operations. When a malicious actor crafts an HTML page specifically engineered to exploit this logic error, they can trick the browser into executing scripts or fetching resources under the authority of a different origin than intended. This bypass effectively neutralizes one of the fundamental security pillars of modern web browsers: the Same-Origin Policy, which is critical for preventing unauthorized access to sensitive data and actions across different domains.
From an operational perspective, this vulnerability allows a remote attacker to conduct sophisticated cross-origin attacks without requiring user interaction beyond visiting a malicious webpage or being redirected via phishing techniques. By bypassing origin checks, the attacker can potentially read cookies, local storage, or other persistent state associated with trusted sites if those resources are fetched in the background context improperly authorized by the flaw. This capability transforms what might otherwise be an isolated script execution into a broader data exfiltration vector. The severity is classified as High because it undermines trust boundaries that developers and users rely on to keep their browsing sessions secure, potentially leading to account takeover or sensitive information leakage depending on the specific targets involved in the crafted attack scenario.
In terms of industry standard classifications, this issue aligns with CWE-269, which denotes Improper Privilege Management, as it involves a failure to enforce proper access controls for background processes. Furthermore, from an offensive security framework perspective such as MITRE ATT&CK, this vulnerability facilitates techniques related to Defense Evasion and Credential Access by allowing scripts to operate outside the normal constraints of their originating domain. The exploitation vector is classified as Remote with Low Complexity because it requires only a crafted web page, making it highly feasible for widespread distribution through compromised websites or malicious advertisements.
To mitigate the risks associated with this vulnerability, users must ensure that Google Chrome is updated to version 157.0.8103.38 or later immediately upon availability. For enterprise environments utilizing managed deployments, administrators should verify that automatic update policies are correctly configured to push these patches to all endpoints without delay. Additionally, developers integrating the Background Fetch API into their applications should review their implementation for any reliance on implicit trust assumptions regarding background task execution contexts and ensure strict adherence to origin validation protocols as defined in current web standards. Security monitoring tools should also be tuned to detect anomalous network requests originating from browser processes that do not match expected domain patterns, providing an additional layer of defense against exploitation attempts while patching is being applied.