CVE-2012-2521 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 through 9 does not properly handle objects in memory, which allows remote attackers to execute arbitrary code by accessing a deleted object, aka "Asynchronous NULL Object Access Remote Code Execution Vulnerability."
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Analysis
by VulDB Data Team • 03/27/2021
The vulnerability identified as CVE-2012-2521 represents a critical memory management flaw in Microsoft Internet Explorer versions 6 through 9, classified under CWE-476 as "NULL Pointer Dereference" and subsequently exploited through asynchronous object access patterns. This vulnerability stems from improper handling of memory objects during the browser's rendering and execution processes, specifically when dealing with deleted objects that remain accessible in memory. The flaw occurs when Internet Explorer attempts to access objects that have been marked for deletion but not yet fully removed from memory, creating a window where malicious code can manipulate these stale references to execute arbitrary commands on the target system.
The technical exploitation of this vulnerability relies on the browser's asynchronous JavaScript execution model where objects may be garbage collected or marked for deletion while still being referenced by active script contexts. Attackers can craft malicious web pages that trigger specific browser behaviors causing objects to be deleted while maintaining references to them, allowing for controlled memory access patterns that ultimately enable code execution. This particular vulnerability is categorized under the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" and T1203 for "Exploitation for Client Execution," demonstrating how attackers leverage browser-based scripting environments to achieve remote code execution through memory corruption techniques.
The operational impact of CVE-2012-2521 is severe as it affects a broad range of Internet Explorer versions that were widely deployed across enterprise and consumer environments during the early 2010s. The vulnerability can be exploited through various attack vectors including malicious websites, phishing emails with embedded web content, or compromised web applications that serve malicious JavaScript payloads. Successful exploitation results in full system compromise where attackers can execute arbitrary code with the privileges of the logged-in user, potentially leading to data theft, system infiltration, or deployment of additional malware. The asynchronous nature of the vulnerability makes detection and prevention particularly challenging as the memory access patterns may not immediately trigger security alerts.
Mitigation strategies for this vulnerability require immediate patch application through Microsoft's security updates, as the flaw cannot be effectively addressed through configuration changes or network filtering alone. Organizations should implement comprehensive browser security policies that include disabling unnecessary scripting features, implementing strict content security policies, and deploying web application firewalls to detect and block malicious content. Additionally, security teams should monitor for indicators of compromise related to this vulnerability, including unusual memory access patterns and JavaScript execution anomalies. The vulnerability's classification as a memory corruption issue aligns with ATT&CK technique T1068 for "Exploitation for Privilege Escalation" and requires layered defensive measures including regular security assessments, employee training on phishing awareness, and maintaining up-to-date security tooling that can detect exploitation attempts targeting memory management flaws in web browsers.