CVE-2021-26411 in Edge
Summary
by MITRE • 03/11/2021
Internet Explorer Memory Corruption Vulnerability
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Analysis
by VulDB Data Team • 05/04/2025
This vulnerability represents a critical memory corruption flaw in Microsoft Internet Explorer that arises from improper handling of memory objects during web page rendering processes. The issue occurs when Internet Explorer attempts to process malformed or maliciously crafted web content that triggers unexpected memory allocation and deallocation sequences. The vulnerability stems from insufficient bounds checking and memory management controls within the browser's rendering engine, specifically affecting how the browser handles dynamic memory allocation for web elements such as JavaScript objects, DOM nodes, and HTML elements. When exploited, this memory corruption can lead to arbitrary code execution with the privileges of the current user, making it particularly dangerous in enterprise environments where users may have elevated access rights.
The technical implementation of this vulnerability involves a classic use-after-free condition where memory allocated to web objects becomes invalid before the application attempts to access it again. This occurs during the processing of complex web pages containing nested objects, dynamic content updates, or malicious scripts that manipulate memory references in unexpected ways. The flaw is particularly insidious because it can be triggered through standard web browsing activities without requiring user interaction beyond visiting a malicious website. Attackers can craft specially designed web pages that exploit this memory corruption by manipulating JavaScript objects, DOM elements, and memory pointers to cause the browser to execute arbitrary code. The vulnerability affects multiple versions of Internet Explorer including IE11 and older versions, with the exploitation vector typically involving crafted HTML content that includes malicious JavaScript or embedded ActiveX controls.
The operational impact of this vulnerability extends beyond simple browser compromise to potentially enable full system takeover in environments where users maintain administrative privileges. Once successfully exploited, the memory corruption allows attackers to execute malicious code with the same privileges as the compromised user, potentially leading to data exfiltration, lateral movement within networks, and persistent backdoor installation. The vulnerability's exploitation does not require specialized tools or extensive knowledge of the underlying system architecture, making it particularly attractive to threat actors seeking to compromise enterprise networks through phishing campaigns or drive-by downloads. Organizations running legacy Internet Explorer installations face significant risk exposure, especially in environments where the browser is still actively used for business-critical applications or where users have unrestricted access to external web content.
Security professionals should implement immediate mitigations including disabling Internet Explorer in enterprise environments where possible, deploying enhanced browser security policies, and ensuring all systems have up-to-date security patches. The vulnerability aligns with attack patterns documented in the attack tree framework where adversaries leverage memory corruption vulnerabilities to establish persistent access and escalate privileges. Organizations should consider implementing web application firewalls, content filtering systems, and network segmentation to reduce the attack surface. Additionally, security teams should monitor for exploitation attempts through network traffic analysis and endpoint detection systems that can identify suspicious memory access patterns. The vulnerability demonstrates the importance of maintaining current browser versions and implementing robust security practices that include regular patch management, user education, and continuous monitoring of system integrity. According to common weakness enumeration standards, this vulnerability maps to CWE-125 out-of-bounds read conditions and CWE-476 null pointer dereference patterns that are commonly exploited in browser-based attacks. Mitigation strategies should also include implementing sandboxing technologies and browser hardening configurations that limit the potential impact of successful exploitation attempts.