CVE-2012-0172 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 through 8 does not properly handle objects in memory, which allows remote attackers to execute arbitrary code by accessing a deleted object, aka "VML Style Remote Code Execution Vulnerability."
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Analysis
by VulDB Data Team • 03/22/2021
The vulnerability identified as CVE-2012-0172 represents a critical memory corruption flaw in Microsoft Internet Explorer versions 6 through 8 that enables remote code execution through improper object handling in memory. This vulnerability specifically affects the Vector Markup Language (VML) processing component within the browser, which is responsible for rendering vector graphics and graphical elements on web pages. The flaw stems from the browser's insufficient validation mechanisms when managing memory objects, particularly those related to VML style processing, creating a scenario where attackers can manipulate memory access patterns to execute malicious code with the privileges of the targeted user.
The technical exploitation of this vulnerability occurs when Internet Explorer encounters malformed VML content that triggers improper memory management during object lifecycle operations. When a VML object is deleted from memory but still referenced by subsequent code execution, the browser's memory management system fails to properly invalidate the object reference, allowing attackers to access the freed memory location. This memory access violation creates a condition where arbitrary code can be executed in the context of the current user session, potentially leading to complete system compromise. The vulnerability operates at the memory management level and aligns with CWE-476, which describes NULL pointer dereference conditions that can lead to arbitrary code execution.
From an operational perspective, this vulnerability presents significant risk to organizations using legacy Internet Explorer versions, as it requires no user interaction beyond visiting a malicious webpage containing crafted VML content. The attack vector is particularly dangerous because it can be delivered through various means including phishing emails, compromised websites, or malicious advertisements, making it difficult to defend against through traditional user awareness measures alone. The vulnerability's impact extends beyond simple code execution, as successful exploitation can lead to full system compromise, data theft, and persistence mechanisms that allow attackers to maintain access to compromised systems. This aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation.
The exploitation process typically involves crafting malicious VML content that triggers the memory corruption condition when processed by the vulnerable browser version. Attackers can leverage this vulnerability to bypass security controls such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) through sophisticated exploitation techniques. Organizations with legacy systems running Internet Explorer 6 through 8 face heightened risk due to the extended support lifecycle of these older browser versions, which makes them more vulnerable to such memory corruption attacks. The vulnerability's classification as a remote code execution flaw means that network-based attacks can be conducted without requiring physical access to target systems, making it particularly attractive to threat actors conducting large-scale campaigns. Mitigation strategies should focus on immediate browser upgrades, implementation of security policies that restrict VML processing, and deployment of network-based protections such as web application firewalls to filter malicious content before it reaches vulnerable systems.