CVE-2013-0093 in Internet Explorer
Summary
by MITRE
Use-after-free vulnerability in Microsoft Internet Explorer 6 through 10 allows remote attackers to execute arbitrary code via a crafted web site that triggers access to a deleted object, aka "Internet Explorer onBeforeCopy Use After Free Vulnerability."
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Analysis
by VulDB Data Team • 05/06/2021
The vulnerability identified as CVE-2013-0093 represents a critical use-after-free flaw in Microsoft Internet Explorer versions 6 through 10 that enables remote code execution through malicious web content. This vulnerability specifically affects the onBeforeCopy event handling mechanism within the browser's JavaScript engine, creating a scenario where memory management errors can be exploited to gain unauthorized system access. The flaw occurs when Internet Explorer processes web pages containing crafted JavaScript code that manipulates object references after they have been freed from memory, allowing attackers to execute arbitrary code with the privileges of the logged-in user. Such vulnerabilities fall under the CWE-416 category of Use After Free conditions, which are classified as severe memory safety issues that can lead to complete system compromise. The ATT&CK framework categorizes this vulnerability under T1059.007 for Windows Command Shell and T1547.001 for Registry Run Keys / Startup Folder, as exploitation typically involves persistent access mechanisms. The vulnerability's impact is particularly severe because it affects multiple versions of Internet Explorer, spanning from IE6 through IE10, which were widely deployed across enterprise environments and personal computers during the affected period. Attackers can craft malicious web pages that trigger the vulnerable code path when users visit compromised websites, making this a prevalent vector for drive-by download attacks and social engineering campaigns.
The technical implementation of this vulnerability relies on the browser's object lifecycle management within the JavaScript engine, specifically when handling the onBeforeCopy event. When Internet Explorer encounters JavaScript code that manipulates objects during or after the copy operation event, the memory management system may prematurely free object references while the script continues to reference them. This creates a race condition where attackers can overwrite freed memory with malicious payloads, effectively allowing code execution. The exploitation process typically involves creating a crafted HTML page that contains JavaScript code triggering the vulnerable event handler, followed by memory corruption techniques that leverage the freed object to redirect execution flow. The vulnerability's presence in multiple IE versions indicates a fundamental flaw in the browser's memory management implementation that was not adequately addressed across the product line. This particular use-after-free scenario is classified as a heap-based vulnerability where freed memory blocks can be reallocated and manipulated by attackers to inject malicious code, representing a classic example of how memory safety issues can be leveraged for privilege escalation and system compromise. The attack surface is particularly broad as it requires no user interaction beyond visiting a malicious website, making it highly effective for automated exploitation campaigns.
The operational impact of CVE-2013-0093 extends beyond simple remote code execution to encompass complete system compromise and persistent access capabilities. Successful exploitation allows attackers to execute arbitrary code with the privileges of the current user, potentially leading to full system takeover, data exfiltration, and establishment of backdoors. Organizations running affected versions of Internet Explorer face significant risk as this vulnerability can be exploited through standard web browsing activities without requiring specialized tools or user interaction beyond visiting malicious websites. The vulnerability's presence in IE6 through IE10 creates an extensive attack surface since these versions were commonly used in enterprise environments, government agencies, and personal computing scenarios where users might not have the latest security updates. Security researchers have documented numerous real-world exploitation attempts leveraging this vulnerability, particularly in targeted attacks against organizations with legacy Internet Explorer deployments. The impact is further amplified by the fact that many organizations were slow to patch or upgrade their Internet Explorer installations, creating prolonged exposure windows for this vulnerability. Organizations may also face compliance and regulatory issues if systems running vulnerable versions are found to be non-compliant with security standards such as those outlined in the NIST Cybersecurity Framework or ISO 27001 requirements for vulnerability management.
Mitigation strategies for CVE-2013-0093 focus on immediate remediation through patch application and long-term architectural changes to reduce attack surface. Microsoft released security updates that addressed this vulnerability through improved memory management in the JavaScript engine, requiring users to apply the relevant patches immediately to prevent exploitation. Organizations should implement comprehensive patch management processes to ensure all Internet Explorer installations are updated with the latest security patches, particularly focusing on legacy versions that may not receive extended support. Browser isolation techniques and application whitelisting can provide additional protection layers, while network-based intrusion detection systems can help identify exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date browser software and implementing security awareness training to prevent users from visiting malicious websites. Organizations should also consider implementing web application firewalls and content filtering solutions to block access to known malicious domains. Regular security assessments and vulnerability scanning should include checks for outdated Internet Explorer installations, as this vulnerability represents a persistent risk for organizations maintaining legacy browser environments. The use of modern browser security features such as sandboxing, memory protection, and automatic updates can significantly reduce the risk of exploitation, while adherence to security best practices such as principle of least privilege and regular security audits helps minimize potential damage from successful attacks.