CVE-2001-0096 in IIS
Summary
by MITRE
FrontPage Server Extensions (FPSE) in IIS 4.0 and 5.0 allows remote attackers to cause a denial of service via a malformed form, aka the "Malformed Web Form Submission" vulnerability.
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Analysis
by VulDB Data Team • 05/06/2019
The vulnerability identified as CVE-2001-0096 represents a critical denial of service flaw within the FrontPage Server Extensions component of Microsoft Internet Information Services versions 4.0 and 5.0. This weakness specifically targets the processing of web form submissions and enables remote attackers to disrupt service availability by exploiting a particular class of malformed input data. The vulnerability resides in the server extension's handling of user input through web forms, making it particularly dangerous in environments where web applications rely heavily on form-based interactions for user engagement and data collection.
The technical implementation of this vulnerability stems from insufficient input validation within the FrontPage Server Extensions module. When the system receives a malformed web form submission, the processing logic fails to properly handle the unexpected data structure, leading to a crash or resource exhaustion that results in complete service disruption. This flaw operates at the application layer and can be triggered through simple HTTP requests containing malformed form data, making it accessible to attackers with minimal technical expertise. The vulnerability specifically affects the way IIS handles form processing within the FPSE framework, where the server extensions are designed to provide enhanced web publishing capabilities but instead become a point of failure when encountering improperly formatted data.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise the availability of web applications hosted on affected servers. Attackers can repeatedly exploit this weakness to maintain ongoing denial of service conditions, potentially causing significant business disruption for organizations relying on their web infrastructure. The vulnerability affects systems where FrontPage Server Extensions are installed and enabled, which were common in enterprise environments during the early 2000s when IIS 4.0 and 5.0 were prevalent. Organizations with web applications that depend on form submissions for user interaction face the highest risk, as the attack can be executed without requiring authentication or specialized tools, making it particularly dangerous in production environments.
Mitigation strategies for this vulnerability should focus on immediate remediation through Microsoft security patches and updates that address the input validation flaws within the FrontPage Server Extensions. System administrators should disable FrontPage Server Extensions on IIS servers where they are not required, as this represents the most effective defense against exploitation. Network segmentation and firewall rules can help limit exposure by restricting access to affected servers, while monitoring systems should be implemented to detect unusual traffic patterns that might indicate exploitation attempts. This vulnerability aligns with CWE-20, which describes improper input validation, and demonstrates how application-level flaws can be exploited to achieve denial of service conditions. The attack pattern follows ATT&CK technique T1499.004, which involves network denial of service attacks, highlighting the importance of proper input sanitization and robust error handling in web server implementations. Organizations should also consider implementing intrusion detection systems to monitor for patterns consistent with this specific vulnerability and ensure that all web server components are regularly updated to prevent exploitation of known weaknesses.