CVE-2015-1684 in Internet Explorer
Summary
by MITRE
VBScript.dll in the Microsoft VBScript 5.6 through 5.8 engine, as used in Internet Explorer 8 through 11 and other products, allows remote attackers to bypass the ASLR protection mechanism via a crafted web site, aka "VBScript ASLR Bypass."
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Analysis
by VulDB Data Team • 05/11/2022
The vulnerability identified as CVE-2015-1684 represents a significant security flaw in Microsoft's VBScript engine that affects Internet Explorer versions 8 through 11 and other applications utilizing the VBScript 5.6 through 5.8 runtime. This vulnerability specifically targets the Address Space Layout Randomization protection mechanism, which is a fundamental security feature designed to prevent exploitation of memory corruption vulnerabilities by randomizing the memory layout of processes. The flaw allows remote attackers to bypass ASLR, effectively undermining one of the primary defenses against exploitation techniques that rely on predictable memory addresses.
The technical implementation of this vulnerability resides within VBScript.dll, the core component responsible for executing VBScript code within Microsoft's Internet Explorer environment. When a malicious website is visited, the crafted script can manipulate the VBScript engine to reveal memory layout information or force predictable memory addresses, thereby defeating the ASLR protection that would normally make exploitation of subsequent memory corruption vulnerabilities significantly more difficult. This bypass occurs through manipulation of the script engine's memory management functions and the way it handles dynamic code execution within the browser context.
The operational impact of this vulnerability is severe as it significantly reduces the security posture of affected systems by enabling more sophisticated attack vectors. Attackers who can successfully bypass ASLR gain the ability to more reliably exploit other vulnerabilities that may exist in the same environment, as they no longer face the randomization barrier that typically makes such exploitation attempts fail. This vulnerability particularly affects enterprise environments where Internet Explorer remains in use, as it can be leveraged to execute arbitrary code on targeted systems, potentially leading to full system compromise, data exfiltration, or lateral movement within networks.
The vulnerability aligns with CWE-119, which addresses "Improper Access to Memory Location" and specifically relates to memory protection bypasses that undermine security mechanisms designed to prevent exploitation. From an ATT&CK framework perspective, this vulnerability maps to T1059.005 for "Command and Scripting Interpreter: Visual Basic" and T1068 for "Exploitation for Privilege Escalation" as it enables attackers to execute malicious scripts that can escalate privileges. Organizations should implement immediate mitigations including disabling VBScript execution in Internet Explorer, applying Microsoft security updates, and deploying additional security controls such as exploit protection policies and network segmentation to reduce the attack surface. The vulnerability underscores the importance of maintaining up-to-date security patches and demonstrates how flaws in scripting engines can have cascading effects on overall system security.