Internet Explorer JScript and VBScript Engines Remote Code Execution Vulnerability (CVE-2016-0189)

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2016-0189) is an Out-of-bounds Write (CWE-787) and memory corruption vulnerability residing in the Microsoft JScript 5.8 and VBScript 5.7/5.8 scripting engines as used by Internet Explorer. The root cause lies in the engines' improper handling of objects in memory during size modification or array manipulation, leading to memory corruption where attackers can read or write outside the intended buffer boundaries.

2. Exploitation Mechanics & Attack Scenario

An attacker exploits this vulnerability by hosting a maliciously crafted webpage containing VBScript or JScript code and enticing users to visit the site (e.g., via spear-phishing). When Internet Explorer renders the page, the script triggers a memory corruption condition—often by abusing VBScript's ReDim statement to resize arrays dynamically. This allows the attacker to bypass the browser's security sandbox, achieve 'God Mode' (arbitrary memory read/write), and execute arbitrary shellcode within the context of the current user.

3. Infrastructure & Business Impact

As a highly critical vulnerability listed in the CISA KEV catalog, CVE-2016-0189 has been actively exploited in the wild by APT groups and integrated into multiple exploit kits. Successful exploitation grants the attacker full control over the compromised endpoint, potentially leading to lateral movement within the corporate network, deployment of ransomware, and exfiltration of sensitive business data.