CVE-2026-121066 in Chrome
Summary
by MITRE • 11/03/2026
Incorrect authorization in Extensions in Google Chrome prior to 157.0.8103.38 allowed a remote attacker leveraging social engineering to bypass system access restrictions via a crafted Chrome extension. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as an incorrect authorization flaw within the Google Chrome Extensions architecture prior to version 157.0.8103.38 represents a significant breach in the browser's permission model, specifically affecting how extensions interact with system-level access controls. This issue stems from a logical error in the validation mechanisms that govern extension privileges, allowing maliciously crafted or compromised extensions to operate beyond their intended scope without triggering appropriate security warnings or denials. The core technical flaw lies in the failure of the authorization subsystem to correctly verify whether an extension possesses the necessary permissions for specific high-risk operations, such as accessing sensitive user data, modifying browser settings, or interacting with other web pages and system resources. This misconfiguration effectively creates a gap between the declared manifest permissions and the actual runtime enforcement, enabling code execution contexts that should be restricted by default security policies to execute with elevated privileges.
From an operational perspective, this vulnerability facilitates remote attacks primarily through social engineering vectors rather than direct exploitation of network services. An attacker typically distributes a malicious Chrome extension disguised as a legitimate utility or tool, relying on the user's trust and lack of technical scrutiny during installation. Once installed, the extension leverages the authorization bypass to perform actions that would normally require explicit user consent or administrative approval. This can include stealing cookies, session tokens, and saved passwords; monitoring browsing activity across all visited sites; injecting malicious scripts into web pages for credential harvesting or drive-by downloads; and potentially exfiltrating sensitive documents stored locally if file system access permissions were improperly granted or bypassed. The severity is classified as medium by the Chromium security team because while it does not allow arbitrary code execution at the operating system level directly, it compromises the confidentiality and integrity of user data within the browser environment, which serves as a primary gateway to broader account takeovers in many modern workflows.
This vulnerability aligns closely with CWE-269, Improper Privilege Assignment, where an actor is granted privileges that are not appropriate for their role or intended function. Furthermore, it maps to MITRE ATT&CK techniques such as T1059 Command and Scripting Interpreter if the extension executes scripts within browser contexts, and more critically T1534 Internal Spearphishing when used in targeted campaigns where a malicious extension is delivered via phishing emails that trick users into installing them. The attack chain often involves initial access through social engineering, followed by persistence as the extension remains installed to maintain ongoing surveillance or data theft capabilities. Defenders must recognize that browser extensions are essentially untrusted code running with significant local privileges, making their security posture critical to overall endpoint hygiene.
Mitigation strategies focus heavily on proactive defense and user education rather than technical patches alone for end-users who cannot immediately update software. Organizations should enforce strict policies regarding the installation of third-party Chrome extensions through enterprise management tools like Google Admin Console or Microsoft Intune, whitelisting only verified and necessary add-ons while blocking all others by default. Users must be trained to scrutinize extension permissions during installation, paying close attention to requests for broad access such as read-and-change-all-data-on-websites-youd-visit which is often abused in these scenarios. Immediate remediation requires updating Google Chrome to version 157.0.8103.38 or later where the authorization logic has been corrected to strictly enforce permission boundaries and validate extension capabilities against declared manifest entries before granting access. Regular auditing of installed extensions, removing unused add-ons, and utilizing browser security features like Site Isolation can further reduce the attack surface by limiting the potential blast radius if a malicious extension is inadvertently installed.