CVE-2010-0491 in Internet Explorer
Summary
by MITRE
Use-after-free vulnerability in Microsoft Internet Explorer 5.01 SP4, 6, and 6 SP1 allows remote attackers to execute arbitrary code by changing unspecified properties of an HTML object that has an onreadystatechange event handler, aka "HTML Object Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 05/04/2026
This vulnerability represents a classic use-after-free flaw in Microsoft Internet Explorer that emerged in versions 5.01 SP4, 6, and 6 SP1, categorized under CWE-416. The vulnerability stems from improper memory management when handling HTML object elements with onreadystatechange event handlers, creating a condition where freed memory regions can be accessed and manipulated by malicious actors. The flaw occurs when an HTML object is destroyed but its memory is not properly invalidated, allowing subsequent operations to reference this freed memory location.
The technical execution of this vulnerability involves manipulating HTML object properties through unspecified means that trigger the memory corruption during the object lifecycle management. Attackers can craft malicious web content that causes Internet Explorer to free an object's memory while maintaining references to it, then subsequently access this freed memory to execute arbitrary code with the privileges of the victim user. This type of memory corruption vulnerability falls under the ATT&CK technique T1059.007 for command and scripting interpreter, as attackers can leverage the compromised browser to execute malicious payloads.
The operational impact of this vulnerability is significant as it enables remote code execution without requiring user interaction beyond visiting a malicious webpage, making it particularly dangerous for enterprise environments where users may inadvertently encounter compromised content. The vulnerability affects a broad range of Internet Explorer versions from the early 2000s, representing a critical security gap that could be exploited by attackers to gain full system control, install malware, or establish persistent access. Organizations running these older browser versions face substantial risk exposure given the widespread use of these legacy systems.
Mitigation strategies should prioritize immediate patching of affected systems with Microsoft security updates, as the vulnerability was addressed through proper memory management implementations in later versions. Browser isolation techniques and network segmentation can provide additional defense layers, while security awareness training helps prevent users from accessing untrusted web content. The vulnerability highlights the importance of regular security updates and proper memory management practices in software development, particularly for applications handling user-supplied content. Organizations should also implement web application firewalls and content filtering solutions to detect and block malicious web requests targeting known vulnerable browser versions.