CVE-2002-0078 in Internet Explorer
Summary
by MITRE
The zone determination function in Microsoft Internet Explorer 5.5 and 6.0 allows remote attackers to run scripts in the Local Computer zone by embedding the script in a cookie, aka the "Cookie-based Script Execution" vulnerability.
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Analysis
by VulDB Data Team • 06/27/2021
The vulnerability described in CVE-2002-0078 represents a critical security flaw in Microsoft Internet Explorer versions 5.5 and 6.0 that fundamentally undermines the browser's security model. This issue specifically targets the zone determination mechanism that Internet Explorer employs to classify web content into different security zones such as Internet, Local Intranet, Trusted Sites, and Local Computer zone. The Local Computer zone is designated for content originating from the local machine or trusted sources and typically grants elevated privileges to scripts executing within it. The flaw allows attackers to bypass these security boundaries by embedding malicious scripts within HTTP cookies, effectively tricking the browser into executing code in a higher privilege zone than intended.
The technical implementation of this vulnerability stems from how Internet Explorer processes cookies and determines their associated security zones. When a web server sends a cookie containing script code, the browser's zone determination function fails to properly validate or sanitize the cookie content before executing any embedded scripts. This occurs because the zone assignment logic does not adequately distinguish between cookies that should be treated as part of the Local Computer zone versus those that should remain in a lower privilege security context. The vulnerability specifically exploits the cookie parsing and execution flow where scripts embedded in cookie values are automatically executed by the browser without proper zone validation, allowing arbitrary code execution with the privileges of the Local Computer zone.
The operational impact of this vulnerability is severe as it provides attackers with a method to execute malicious code on vulnerable systems without requiring user interaction beyond visiting a malicious website. This allows for privilege escalation attacks where attackers can execute scripts with local system privileges, potentially leading to complete system compromise. The vulnerability affects a wide range of users since Internet Explorer 5.5 and 6.0 were widely deployed in corporate and enterprise environments during the early 2000s, making this attack vector particularly dangerous. The cookie-based nature of the exploit also makes it difficult to detect through traditional network monitoring since the malicious content is embedded within legitimate HTTP cookie headers.
From a cybersecurity perspective, this vulnerability aligns with CWE-1030, which describes the improper neutralization of dangerous scripts in cookie values, and maps to ATT&CK technique T1059.007 for scripting languages and T1068 for exploit development. The attack chain typically involves an attacker setting up a malicious web server that sends specially crafted cookies containing malicious scripts to victims who have Internet Explorer 5.5 or 6.0 installed. Once the victim's browser processes these cookies and executes the embedded scripts, the attacker gains the ability to perform actions such as file system access, registry modifications, and other system-level operations that would normally be restricted in lower security zones. The vulnerability demonstrates a fundamental flaw in browser security architecture where cookie handling does not properly enforce security boundaries, representing a classic example of inadequate input validation and privilege management in web browser implementations.
Organizations affected by this vulnerability should implement immediate mitigations including upgrading to newer versions of Internet Explorer that have fixed this issue, disabling cookie support for potentially malicious sites, or implementing network-level controls that can detect and block suspicious cookie content. Microsoft released patches addressing this vulnerability in subsequent security updates, and administrators should ensure all systems are properly patched. The broader security community recognized this vulnerability as an example of how seemingly innocuous features like cookie handling can introduce critical security risks when not properly integrated with the browser's security model, emphasizing the importance of comprehensive security testing for all browser components including those that handle user data and session management functions.