CVE-2016-1638 in Chrome
Summary
by MITRE
extensions/renderer/resources/platform_app.js in the Extensions subsystem in Google Chrome before 49.0.2623.75 does not properly restrict use of Web APIs, which allows remote attackers to bypass intended access restrictions via a crafted platform app.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability described in CVE-2016-1638 resides within the Extensions subsystem of Google Chrome, specifically in the platform_app.js file that manages extension resources. This flaw represents a critical access control bypass issue that undermines the security model designed to protect users from malicious extensions. The vulnerability affects Chrome versions prior to 49.0.2623.75 and stems from insufficient validation of Web API usage within platform applications, which are privileged extensions that operate with elevated permissions and access to system resources.
The technical implementation flaw occurs when Chrome fails to properly enforce restrictions on Web APIs that platform apps can access. This improper restriction allows malicious actors to craft specially designed platform applications that can circumvent intended access controls and gain unauthorized access to system resources or user data. The vulnerability specifically targets the platform app extension model where extensions are granted elevated privileges but should be limited in their API access. This bypass mechanism operates through the manipulation of extension resource handling and API invocation sequences that should normally be restricted.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables attackers to create platform apps that can access restricted system resources, potentially leading to data exfiltration, system compromise, or persistent access. Attackers can leverage this vulnerability to craft malicious extensions that appear legitimate but contain hidden functionality to exploit the relaxed API restrictions. The implications are particularly severe because platform apps are designed to have broad system access for legitimate purposes, making this bypass particularly dangerous as it allows attackers to operate within the trusted extension framework while executing unauthorized actions.
This vulnerability aligns with CWE-284 Access Control Bypass, where insufficient access controls allow unauthorized access to resources or functionality. The flaw also maps to ATT&CK technique T1103, which involves gaining system privileges through legitimate system tools or frameworks. The attack vector typically involves delivering a malicious extension through the Chrome Web Store or via direct installation, where the crafted platform app exploits the API restriction bypass to execute unauthorized operations. Organizations should implement immediate mitigations including mandatory Chrome updates to version 49.0.2623.75 or later, regular security audits of installed extensions, and monitoring for suspicious extension behavior. Additionally, administrators should consider implementing extension whitelisting policies and restricting extension installation permissions to minimize the risk of exploitation. The vulnerability highlights the importance of proper API access control enforcement in privileged extension frameworks and demonstrates the critical need for comprehensive security testing of extension subsystems.