CVE-2011-2019 in Internet Explorer
Summary
by MITRE
Untrusted search path vulnerability in Microsoft Internet Explorer 9 on Windows Server 2008 R2 and R2 SP1 and Windows 7 Gold and SP1 allows local users to gain privileges via a Trojan horse DLL in the current working directory, as demonstrated by a directory that contains an HTML file, aka "Internet Explorer Insecure Library Loading Vulnerability."
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Analysis
by VulDB Data Team • 03/20/2021
This vulnerability represents a classic insecure library loading flaw that affects Microsoft Internet Explorer 9 on specific Windows operating systems including Windows Server 2008 R2 and R2 SP1, as well as Windows 7 Gold and SP1. The issue stems from Internet Explorer's failure to properly validate the search path when loading dynamic link libraries, creating an opportunity for privilege escalation attacks. The vulnerability is categorized under CWE-427 Uncontrolled Search Path Element, which specifically addresses situations where applications search for libraries in predictable locations without proper validation. This flaw enables attackers to place malicious DLL files in directories that are searched before system directories, allowing them to inject code with elevated privileges.
The attack vector involves a local user placing a specially crafted Trojan horse DLL in the current working directory where an HTML file is located. When Internet Explorer processes this HTML file, it attempts to load required libraries from the current directory first, before checking system directories. This behavior violates the principle of least privilege and creates a predictable exploitation pattern. The vulnerability is particularly dangerous because it leverages the trust relationship between the browser and the local file system, allowing an attacker to execute arbitrary code with the privileges of the logged-in user. This aligns with ATT&CK technique T1059 Command and Scripting Interpreter, where adversaries use system processes to execute malicious code.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to establish persistent access, escalate privileges to SYSTEM level, and potentially compromise entire systems. The attack requires local access to the target system, making it a local privilege escalation vulnerability that can be exploited by any user with access to the system. This creates a significant risk in environments where multiple users have access to shared systems or where users have legitimate administrative access that could be compromised. The vulnerability affects all versions of Internet Explorer 9 on the targeted operating systems, making it particularly concerning given the widespread use of these browsers. The exploitability is enhanced by the fact that users often have the ability to create files in directories where HTML content is stored, making the attack surface broader than initially apparent.
Mitigation strategies for this vulnerability include applying Microsoft security patches immediately, which address the root cause by implementing proper library loading validation. System administrators should also implement the principle of least privilege by limiting user access to directories where HTML content is stored and ensuring that system directories are prioritized in library search paths. Additional protective measures include enabling Windows Defender Application Control policies, implementing strict directory permissions, and conducting regular security audits to identify and remove potentially malicious DLL files from user-accessible directories. Organizations should also consider implementing application whitelisting solutions to prevent unauthorized DLL loading. The vulnerability highlights the importance of secure coding practices and proper validation of library paths, particularly in applications that handle user-supplied content, as outlined in security best practices for secure software development lifecycle processes.