CVE-2000-0884 in IIS
Summary
by MITRE
IIS 4.0 and 5.0 allows remote attackers to read documents outside of the web root, and possibly execute arbitrary commands, via malformed URLs that contain UNICODE encoded characters, aka the "Web Server Folder Traversal" vulnerability.
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Analysis
by VulDB Data Team • 10/12/2025
The CVE-2000-0884 vulnerability represents a critical directory traversal flaw in Microsoft Internet Information Services versions 4.0 and 5.0 that fundamentally compromises web server security through improper URL handling mechanisms. This vulnerability specifically exploits the web server's failure to properly validate and sanitize UNICODE encoded characters within incoming requests, creating a pathway for malicious actors to access files and directories outside the intended web root boundaries. The flaw operates at the core of the web server's request processing pipeline where UNICODE character sequences are not adequately normalized or filtered before path resolution occurs.
The technical implementation of this vulnerability stems from the web server's inadequate input validation routines that fail to properly decode and sanitize UNICODE sequences in URLs. When a maliciously crafted URL containing UNICODE encoded characters is processed, the server's path resolution algorithm interprets these sequences in ways that bypass normal access controls and directory restrictions. This allows attackers to construct requests that appear to target legitimate web content while actually referencing files in system directories outside the web root. The vulnerability is particularly dangerous because it leverages the inherent complexity of UNICODE character encoding where multiple representations of the same character can exist, creating opportunities for attackers to craft requests that evade detection while maintaining their malicious intent.
The operational impact of CVE-2000-0884 extends far beyond simple information disclosure, as it provides attackers with the capability to read sensitive system files, configuration data, and potentially execute arbitrary code on the affected servers. This vulnerability directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The ability to read files outside the web root means attackers can access critical system information such as password files, configuration settings, database connection strings, and other sensitive data that could facilitate further compromise of the system. In many cases, this vulnerability can serve as a stepping stone for more sophisticated attacks, potentially allowing privilege escalation or lateral movement within the network infrastructure.
The attack vector for this vulnerability is particularly insidious because it requires minimal privileges and can be executed through standard web browser interactions. Attackers can craft malicious URLs containing UNICODE sequences that, when processed by the vulnerable IIS server, result in unauthorized file access. The vulnerability's classification under the ATT&CK framework aligns with techniques such as T1059 for command and scripting interpreter and T1566 for credential access through social engineering, as it enables attackers to gather system information and potentially escalate privileges. Organizations running vulnerable IIS versions face significant risk exposure, as the vulnerability can be exploited through simple HTTP requests without requiring special tools or advanced technical knowledge, making it a preferred target for both automated scanning tools and manual exploitation attempts.
Mitigation strategies for CVE-2000-0884 require immediate implementation of both software patches and configuration hardening measures. Microsoft released security updates specifically addressing this vulnerability, and organizations should prioritize deployment of these patches to remediate the core flaw. Additionally, network administrators should implement URL filtering mechanisms that normalize and sanitize UNICODE characters in incoming requests, while also configuring proper access controls and directory restrictions. The implementation of web application firewalls and intrusion prevention systems can provide additional layers of protection by detecting and blocking suspicious URL patterns. Organizations should also conduct comprehensive security assessments to identify any remaining vulnerable systems and ensure that all web server configurations adhere to security best practices, including regular monitoring for unauthorized access attempts and maintaining up-to-date security information exchange protocols to stay informed about similar vulnerabilities.