CVE-2026-106331 in Chrome
Summary
by MITRE • 10/07/2026
Improper input validation in Extensions in Google Chrome prior to 155.0.8059.39 allowed a remote attacker leveraging social engineering to bypass web origin policy into a privileged page via a crafted Chrome extension. (Chromium security severity: Low)
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified as an improper input validation flaw within Google Chrome extensions prior to version 155.0.8059.39 represents a significant breach in the browser's isolation mechanisms, specifically targeting the boundary between untrusted web content and privileged extension pages. This security defect allows for the bypass of the Web Origin Policy, a fundamental security feature designed to restrict how documents or scripts loaded from one origin can interact with resources from another origin. By exploiting this flaw, an attacker who has successfully deployed a malicious Chrome extension through social engineering tactics can execute code within the context of privileged pages that are typically shielded from standard web page access. The Chromium project has classified this issue with a Low security severity rating, indicating that while the technical execution requires specific conditions such as user interaction and installation of the extension, the potential for privilege escalation remains a critical concern for users who may inadvertently grant permissions to untrusted software.
From a technical perspective, the root cause lies in insufficient validation of inputs passed between different components of the Chrome architecture or within the extension's own code execution environment. When an extension interacts with privileged APIs or accesses internal browser pages, it must adhere to strict origin checks and input sanitization protocols. In this instance, the failure to properly validate these inputs allowed crafted data structures to manipulate the execution context, effectively tricking the browser into treating untrusted web-originated scripts as if they were originating from a trusted extension background page or popup. This bypass enables the attacker to access sensitive information stored in local storage, cookies, or other privileged states that are normally inaccessible to standard websites due to same-origin policy restrictions. The attack vector relies heavily on social engineering because it requires the victim user to actively install and enable the malicious extension, thereby granting it the necessary permissions to operate within its elevated context before the vulnerability can be leveraged for further exploitation.
The operational impact of this vulnerability is primarily centered around data exfiltration and potential session hijacking if combined with other techniques such as cross-site scripting or cookie theft. Although the severity is rated low due to the prerequisite of user interaction, the ability to bypass origin policies into privileged pages means that an attacker could potentially read sensitive extension-specific data, manipulate browser settings controlled by extensions, or use the trusted context to perform actions on behalf of the user without their knowledge. This undermines the trust model upon which web browsers are built, where users rely on the separation between untrusted web content and trusted application interfaces. The existence of such a flaw highlights the risks associated with third-party software integration in security-critical applications like web browsers, where even minor validation oversights can lead to significant privilege escalations when combined with user deception tactics.
To mitigate this risk, users are strongly advised to update Google Chrome immediately to version 155.0.8059.39 or later, which contains the necessary patches for improper input validation in extensions. Beyond updating software, security best practices dictate that users should exercise extreme caution when installing browser extensions, reviewing permissions carefully and only trusting sources from verified developers with strong reputations. Administrators managing enterprise environments should implement strict extension whitelisting policies to prevent unauthorized or unvetted extensions from being installed on employee devices. Additionally, monitoring for unusual network traffic originating from browser processes can help detect potential exploitation attempts in real-time. The industry standard classification for this type of vulnerability aligns with CWE-20 Improper Input Validation and relates to ATT&CK techniques involving Initial Access via Trusted Software Distribution or Social Engineering, emphasizing the need for both technical controls and user awareness training to defend against such threats.