Microsoft Internet Explorer and Windows Internet Messaging API Information Disclosure Vulnerability (CVE-2016-3298)

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2016-3298) exists in Microsoft Internet Explorer 9 through 11 and the Windows Internet Messaging API. The root cause lies in the improper handling of resource validation requests when accessing local file paths. The browser fails to properly isolate error responses or execution timing differences when attempting to access local system resources.

2. Exploitation Mechanics & Attack Scenario

An attacker hosts a malicious web page containing crafted JavaScript code. When a target user visits the site, the script attempts to load local resources using specific protocols (such as res://) or API calls. By measuring the differences in event triggers (e.g., timing or specific error codes returned via onload/onerror handlers), the script determines whether specific files or directories exist on the victim's local drive.

3. Infrastructure & Business Impact

While this is an information disclosure vulnerability that does not directly allow remote code execution, it serves as a critical reconnaissance vector. Attackers leverage this flaw to map out installed security software, operating system configurations, and third-party applications, enabling them to craft highly targeted and successful follow-up exploits. Its inclusion in the CISA KEV catalog highlights its historical and practical significance in real-world attack campaigns.