CVE-2001-0902 in IIS
Summary
by MITRE
Microsoft IIS 5.0 allows remote attackers to spoof web log entries via an HTTP request that includes hex-encoded newline or form-feed characters.
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Analysis
by VulDB Data Team • 05/31/2019
Microsoft Internet Information Services version 5.0 contains a vulnerability that enables remote attackers to manipulate web server log entries through carefully crafted HTTP requests. This flaw stems from insufficient input validation of HTTP request headers and parameters, specifically failing to properly sanitize or filter hex-encoded newline characters such as carriage return and line feed sequences. The vulnerability operates at the application layer where HTTP requests are processed and logged, creating a potential vector for log manipulation and audit trail corruption. When an attacker submits an HTTP request containing hex-encoded newline or form-feed characters, the web server processes these sequences and incorporates them into the log file entries, effectively allowing the attacker to inject malicious content or alter the appearance of legitimate log records.
The technical implementation of this vulnerability involves the web server's logging mechanism failing to properly handle or escape special characters during the parsing of incoming HTTP requests. According to CWE-117, this represents a weakness in output processing where improper sanitization of user-supplied data leads to log injection attacks. The vulnerability specifically affects the logging functionality of IIS 5.0, where the server's inability to distinguish between legitimate control characters and maliciously injected ones creates opportunities for attackers to craft requests that modify log entries. This issue falls under the broader category of log forging vulnerabilities that have been documented in various web application security frameworks and represent a significant concern for system administrators seeking to maintain accurate audit trails.
The operational impact of this vulnerability extends beyond simple log manipulation, as it can enable more sophisticated attack vectors including log poisoning, audit evasion, and potentially information disclosure. Attackers can exploit this weakness to hide their activities within legitimate-looking log entries, making it difficult for security monitoring systems to detect malicious behavior. The vulnerability directly impacts the integrity of system audit trails, which are critical for security incident response, compliance auditing, and forensic analysis. Organizations relying on IIS 5.0 for web hosting may find their security monitoring capabilities compromised, as attackers can potentially inject false entries that obscure legitimate activities or create confusion in log analysis processes.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and sanitization at all points where user-supplied data enters the system. Organizations should consider upgrading to newer versions of IIS that have addressed this vulnerability through improved logging mechanisms and enhanced input filtering. The implementation of web application firewalls and intrusion detection systems can provide additional protection by monitoring for suspicious character sequences in HTTP requests. Security configurations should include regular log file monitoring and validation to detect anomalies that may indicate log injection attempts. According to ATT&CK framework category T1070.002, adversaries may use log manipulation techniques to evade detection, making this vulnerability particularly concerning for organizations that depend on accurate logging for security operations. System administrators should also implement proper access controls and monitoring for log files to prevent unauthorized modification and ensure the integrity of audit trails.