CVE-2016-3353 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 9 through 11 mishandles .url files from the Internet zone, which allows remote attackers to bypass intended access restrictions via a crafted file, aka "Internet Explorer Security Feature Bypass."
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Analysis
by VulDB Data Team • 09/16/2022
Microsoft Internet Explorer versions 9 through 11 contained a critical security flaw that allowed remote attackers to bypass intended access restrictions when processing .url files from the Internet zone. This vulnerability stems from how Internet Explorer handles shortcut files that contain URL references, specifically when these files originate from untrusted web sources. The flaw exists in the browser's security model where it fails to properly validate the origin and trust level of .url files, enabling malicious actors to craft specially formatted files that can execute code or access restricted resources. The vulnerability is categorized under CWE-284, which addresses improper access control mechanisms, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter. When a user encounters a crafted .url file from the Internet zone, the browser's security context allows the file to be processed with elevated privileges, bypassing the normal sandboxing protections that should prevent such operations. This creates a dangerous situation where attackers can exploit the trust relationship between the browser and local system resources.
The technical implementation of this vulnerability involves the manipulation of .url file structures that contain specific formatting elements which cause Internet Explorer to improperly interpret the file's security context. These files can contain embedded scripts or references to malicious resources that are executed with the privileges of the user running the browser. The flaw specifically impacts the way Internet Explorer evaluates the security zone of incoming files, particularly when these files are processed through the Windows Shell integration that handles .url file associations. Attackers can leverage this bypass to execute arbitrary code on vulnerable systems, potentially leading to full system compromise. The vulnerability is particularly dangerous because it exploits the trust relationship between the browser and Windows file handling mechanisms, allowing attackers to circumvent the security boundaries that normally protect against malicious file execution from web sources.
The operational impact of CVE-2016-3353 extends beyond simple privilege escalation, as it enables attackers to perform sophisticated attacks that can lead to complete system compromise. Organizations with users running vulnerable versions of Internet Explorer face significant risk when browsing untrusted websites, as simply visiting a malicious site could result in automatic execution of malicious .url files. The vulnerability can be exploited through various attack vectors including phishing campaigns, malicious advertisements, or compromised websites that deliver the crafted files. Security researchers have documented cases where this vulnerability was used in targeted attacks against enterprise networks, where the initial compromise occurred through a single malicious .url file that was downloaded and executed automatically. The attack chain typically begins with a user visiting a compromised website, which then delivers a malicious .url file that exploits the security bypass to gain elevated privileges on the system. This vulnerability has been widely used in advanced persistent threat campaigns where attackers leverage the trust relationships in Windows file handling to establish persistent access to compromised systems.
Mitigation strategies for CVE-2016-3353 focus on both immediate defensive measures and long-term architectural improvements. Organizations should immediately update to patched versions of Internet Explorer or migrate to supported browser alternatives that do not contain this vulnerability. Microsoft released security updates that addressed the specific flaw in how .url files are processed, particularly by strengthening the validation of file origins and security zones. System administrators should also implement additional security controls such as disabling automatic execution of .url files from untrusted sources, configuring browser security settings to restrict Internet zone access to local resources, and implementing network-based protections that can detect and block malicious .url file delivery. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates the critical nature of browser security models in protecting against attacks that exploit trust relationships between system components. Organizations should also consider implementing application whitelisting policies that restrict which files can be executed automatically and monitor for suspicious .url file activity on their networks. Regular security assessments should include testing for the presence of vulnerable browser versions and ensure that all systems are running patched software to prevent exploitation of this and similar security bypass vulnerabilities.