CVE-2001-0508 in IIS
Summary
by MITRE
Vulnerability in IIS 5.0 allows remote attackers to cause a denial of service (restart) via a long, invalid WebDAV request.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability identified as CVE-2001-0508 represents a critical denial of service weakness within Microsoft Internet Information Services version 5.0 that specifically targets the WebDAV protocol implementation. This flaw manifests when the web server processes malformed WebDAV requests containing excessive data sequences that exceed normal processing limits. The vulnerability operates at the application layer of the network stack and exploits the server's insufficient input validation mechanisms for handling extended request parameters. Systems running IIS 5.0 with WebDAV functionality enabled are particularly susceptible to this attack vector, as the server lacks proper bounds checking for incoming request data. The flaw stems from inadequate error handling within the WebDAV extension module, which fails to gracefully manage oversized or malformed requests that could potentially trigger memory corruption or resource exhaustion conditions.
The technical exploitation of this vulnerability involves crafting a specially formatted WebDAV request containing an abnormally long sequence of characters or malformed data structures that exceed the server's internal buffer limits. When IIS 5.0 processes such requests, the server's request parsing logic becomes overwhelmed by the excessive data, leading to a cascading failure that ultimately results in the web server process terminating and restarting automatically. This behavior creates a persistent denial of service condition that can be easily exploited by remote attackers without requiring authentication or specialized privileges. The vulnerability is classified under CWE-129 as an insufficient input validation issue, specifically related to improper validation of input length or size parameters. The attack mechanism operates through the standard HTTP WebDAV protocol extensions, making it particularly dangerous as it can be launched from any network location with access to the target server's web interface.
The operational impact of CVE-2001-0508 extends beyond simple service interruption to encompass significant business continuity risks for organizations relying on IIS 5.0 servers. When exploited successfully, the vulnerability can cause repeated server restarts that disrupt legitimate user access and potentially lead to data loss or corruption during the restart process. The automated nature of the restart process means that attackers can maintain persistent disruption without requiring continuous attack efforts, making this vulnerability particularly effective for sustained denial of service attacks. Organizations may experience increased system administration overhead as IT staff must repeatedly restore services and investigate the root causes of recurring server restarts. The vulnerability also creates opportunities for attackers to use this as a stepping stone for further exploitation attempts, as the server restart may temporarily disable certain security mechanisms or create windows of opportunity for additional attacks. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, specifically targeting the availability aspect of the CIA triad.
Mitigation strategies for CVE-2001-0508 should prioritize immediate patching of affected IIS 5.0 installations with Microsoft security updates or applying the appropriate service packs that address the WebDAV processing flaws. Organizations should implement network-level restrictions to limit access to WebDAV endpoints where possible, particularly by blocking unnecessary HTTP methods such as PROPFIND, PROPPATCH, and MKCOL that are commonly exploited in this type of attack. Network administrators should deploy intrusion detection systems that can identify and block malformed WebDAV requests based on signature patterns or anomaly detection algorithms. Additionally, implementing request rate limiting and connection throttling mechanisms can help prevent the exploitation of this vulnerability by limiting the volume of requests that can be processed within a given time period. The recommended defense in depth approach includes disabling WebDAV functionality entirely if it is not required for business operations, as this eliminates the attack surface entirely. Organizations should also consider implementing application firewalls or web application firewalls that can filter malicious WebDAV requests before they reach the IIS server, providing an additional layer of protection against this specific vulnerability while maintaining necessary functionality for legitimate users.