CVE-2002-0022 in Internet Explorer
Summary
by MITRE
Buffer overflow in the implementation of an HTML directive in mshtml.dll in Internet Explorer 5.5 and 6.0 allows remote attackers to execute arbitrary code via a web page that specifies embedded ActiveX controls in a way that causes 2 Unicode strings to be concatenated.
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Analysis
by VulDB Data Team • 06/27/2021
The vulnerability identified as CVE-2002-0022 represents a critical buffer overflow flaw within the mshtml.dll component of Internet Explorer versions 5.5 and 6.0. This issue stems from the improper handling of HTML directives that contain embedded ActiveX controls, creating a scenario where malicious web pages can exploit memory corruption vulnerabilities to execute arbitrary code on affected systems. The flaw specifically manifests when the browser processes Unicode strings that are concatenated during the parsing of HTML content, leading to memory boundaries being exceeded and potentially allowing attackers to overwrite critical memory locations.
The technical implementation of this vulnerability leverages the way Internet Explorer's mshtml.dll library manages memory allocation for Unicode string operations when processing ActiveX controls within HTML documents. When a web page contains carefully crafted HTML directives that embed ActiveX components, the parsing logic fails to properly validate the length of concatenated Unicode strings, resulting in a classic buffer overflow condition. This memory corruption occurs because the application does not adequately check bounds before performing string concatenation operations, allowing attacker-controlled data to overflow into adjacent memory regions. The vulnerability operates at the application level within the browser's rendering engine, making it particularly dangerous as it can be triggered simply by visiting a malicious website without requiring any user interaction beyond normal browsing behavior.
From an operational perspective, this vulnerability presents a severe threat to enterprise environments as it enables remote code execution without user interaction, making it particularly attractive to attackers seeking to compromise systems. The attack vector requires only that a user visits a malicious web page containing specially crafted HTML content, which then triggers the buffer overflow in the mshtml.dll component. This allows attackers to execute arbitrary code with the privileges of the logged-in user, potentially leading to complete system compromise. The vulnerability affects both Internet Explorer 5.5 and 6.0 versions, representing a significant portion of the browser market at the time of disclosure, and the exploit can be delivered through various means including phishing attacks, compromised websites, or malicious advertisements. Security researchers have classified this as a high-risk vulnerability due to its remote exploitability and the potential for privilege escalation.
Organizations affected by this vulnerability should implement immediate mitigation strategies including applying the relevant Microsoft security patches that address the buffer overflow in mshtml.dll, disabling ActiveX controls in Internet Explorer if not essential for business operations, and implementing network-level protections such as web application firewalls to filter malicious content. The vulnerability aligns with CWE-121, which describes the classic stack-based buffer overflow condition, and represents a technique commonly used in the ATT&CK framework under the T1059.007 category for command and script interpreter execution. Additionally, network administrators should consider implementing security measures such as disabling the automatic execution of ActiveX controls, using security zones to restrict ActiveX behavior, and deploying intrusion detection systems to monitor for exploitation attempts. The long-term solution requires comprehensive patch management processes and user education to avoid visiting untrusted websites that may contain malicious content designed to exploit this and similar vulnerabilities in web browsers.