CVE-2002-0191 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 5.01, 5.5 and 6.0 allows remote attackers to view arbitrary files that contain the "{" character via script containing the cssText property of the stylesheet object, aka "Local Information Disclosure through HTML Object" vulnerability.
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Analysis
by VulDB Data Team • 06/14/2025
The CVE-2002-0191 vulnerability represents a significant local information disclosure flaw in Microsoft Internet Explorer versions 5.01, 5.5, and 6.0 that exploits the browser's handling of CSS stylesheet objects. This vulnerability specifically leverages the cssText property of stylesheet objects to enable remote attackers to access arbitrary files containing the "{" character, effectively bypassing normal file access restrictions. The flaw operates through a sophisticated manipulation of the browser's rendering engine and CSS processing capabilities, creating a pathway for unauthorized file enumeration and content retrieval.
The technical mechanism behind this vulnerability involves the improper validation of CSS content within Internet Explorer's stylesheet object model. When the browser processes HTML content containing specific CSS properties, particularly those utilizing the cssText attribute, it fails to adequately sanitize or validate the input before attempting to render or process the associated stylesheet. This processing error creates a condition where the browser's stylesheet parser can be tricked into accessing local file system resources through carefully crafted script code that references the cssText property of stylesheet objects. The vulnerability specifically targets files that contain the "{" character, which serves as a trigger for the exploitable parsing behavior.
From an operational perspective, this vulnerability poses a severe risk to web application security and user privacy, as it enables attackers to potentially access sensitive local files that should normally be restricted from web-based access. The impact extends beyond simple information disclosure to potentially allow attackers to gather system information, access configuration files, or retrieve other sensitive data that might contain credentials or system details. The vulnerability's remote nature means that attackers can exploit it without requiring physical access to the target system, making it particularly dangerous in web-facing environments where users might encounter malicious content through various attack vectors including phishing, compromised websites, or social engineering campaigns.
The vulnerability maps directly to CWE-200, which describes improper output neutralization for logs, and CWE-20, which covers input validation issues. It also aligns with ATT&CK technique T1059.007 for command and scripting interpreter, and T1566 for phishing attacks, as it enables attackers to create malicious content that can be delivered through web-based attack vectors. Organizations utilizing affected Internet Explorer versions face significant risk of data breaches, system compromise, and potential lateral movement within networks, as this vulnerability can be combined with other attack techniques to create more sophisticated exploitation scenarios.
Mitigation strategies for CVE-2002-0191 should prioritize immediate patch deployment for affected Internet Explorer versions, as Microsoft has released security updates addressing this specific vulnerability. Network administrators should implement strict content filtering and web application firewalls to prevent access to potentially malicious content that could exploit this vulnerability. Browser hardening measures including disabling unnecessary scripting capabilities and implementing strict security policies for stylesheet processing can provide additional defense layers. Organizations should also conduct comprehensive security assessments to identify any web applications or services that might be vulnerable to similar exploitation patterns, and implement proper input sanitization and output validation procedures to prevent similar issues in custom web applications. The vulnerability underscores the importance of maintaining up-to-date browser security patches and implementing defense-in-depth strategies to protect against sophisticated cross-site scripting and local information disclosure attacks.