CVE-2026-121171 in Chrome
Summary
by MITRE • 11/03/2026
Confused deputy in DevTools in Google Chrome prior to 157.0.8103.38 allowed a remote attacker leveraging social engineering to bypass web origin policy via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified as a confused deputy flaw within the DevTools component of Google Chrome prior to version 157.0.8103.38 represents a significant deviation from expected access control behaviors, specifically targeting the web origin policy. This class of security issue arises when an application grants privileges to a user or process that does not have the necessary authorization for certain actions, often because the system fails to properly distinguish between different levels of privilege within its own operations. In this specific instance, the DevTools interface, which is primarily intended for developers and debugging purposes, was exploited in a manner that allowed it to act on behalf of a user without sufficient verification of intent or context. The core technical flaw lies in the improper validation of requests originating from web pages interacting with the browser's internal development tools, leading to an unauthorized elevation of privileges within the browser environment.
The operational impact of this vulnerability is centered around the bypassing of the same-origin policy, a critical security mechanism designed to isolate potentially malicious scripts running on different websites. By leveraging social engineering techniques, a remote attacker could craft a deceptive HTML page that tricks a victim into interacting with it in a way that triggers the confused deputy condition within DevTools. Once triggered, this interaction allows the crafted script to perform actions or access data across origins that should strictly be prohibited by browser security boundaries. This effectively neutralizes one of the primary defenses against cross-site scripting and other web-based attacks, potentially allowing an attacker to read sensitive information from other domains, manipulate session tokens, or execute unauthorized commands within the context of a victim's active browsing sessions.
The reliance on social engineering highlights that this vulnerability is not purely technical in its exploitation vector but requires user interaction to be effective. An attacker must convince a target to visit a malicious webpage and potentially engage with browser features or extensions that interact with DevTools APIs. This human element makes detection difficult through automated means alone, as the traffic may appear legitimate until the specific sequence of events leading to the privilege escalation occurs. The Chromium security team has classified this issue with a medium severity rating, reflecting its potential for significant data exposure while acknowledging the dependency on user interaction and the availability of mitigations such as keeping browsers updated.
To mitigate the risks associated with this vulnerability, users are strongly advised to update Google Chrome immediately to version 157.0.8103.38 or later, where these access control checks have been hardened. Beyond software updates, security best practices dictate that users should remain vigilant against unsolicited links and suspicious web content, particularly those requesting elevated permissions or unusual interactions with browser developer tools. Organizations should also consider implementing strict Content Security Policies to limit the capabilities of scripts running in their environments and restrict the use of DevTools features for non-developer accounts where possible. Aligning these practices with industry standards such as CWE-269, which covers improper privilege management, helps ensure that applications maintain robust boundaries between different trust levels. Furthermore, understanding this attack vector through the lens of MITRE ATT&CK techniques related to browser exploitation and social engineering can aid in developing more effective monitoring and detection strategies for similar future incidents.