CVE-2002-0147 in IIS
Summary
by MITRE
Buffer overflow in the ASP data transfer mechanism in Internet Information Server (IIS) 4.0, 5.0, and 5.1 allows remote attackers to cause a denial of service or execute code, aka "Microsoft-discovered variant of Chunked Encoding buffer overrun."
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Analysis
by VulDB Data Team • 09/22/2025
The vulnerability identified as CVE-2002-0147 represents a critical buffer overflow flaw within the Active Server Pages (ASP) data transfer mechanism of Microsoft Internet Information Server versions 4.0, 5.0, and 5.1. This security weakness specifically targets the chunked encoding implementation that is used to process HTTP requests, creating a pathway for malicious actors to exploit the server's memory handling capabilities. The vulnerability was discovered by Microsoft itself, indicating its significance within the organization's security assessment processes and highlighting the potential for widespread impact across affected systems. The flaw manifests when the IIS server processes HTTP requests that contain specially crafted chunked encoding data, leading to memory corruption that can be leveraged for malicious purposes.
The technical nature of this buffer overflow stems from inadequate input validation within the ASP processing components of IIS, particularly when handling chunked HTTP transfer encoding. When the server receives HTTP requests containing malformed chunked data, the ASP engine fails to properly bounds-check the data before copying it into fixed-size buffers, resulting in memory corruption that can overwrite adjacent memory locations. This particular implementation flaw falls under the CWE-121 category of "Stack-based Buffer Overflow" and aligns with the broader class of buffer overflow vulnerabilities that have been extensively documented in the cybersecurity community. The chunked encoding mechanism itself is a legitimate HTTP feature designed to handle large data transfers efficiently, but the improper implementation in these IIS versions creates a dangerous scenario where legitimate protocol usage becomes a vector for exploitation.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it provides attackers with the capability to execute arbitrary code on vulnerable systems. This represents a severe escalation from basic availability attacks to full system compromise, enabling threat actors to gain unauthorized access, install malware, or establish persistent backdoors. The vulnerability affects systems running IIS 4.0, 5.0, and 5.1 across various Windows operating systems, making it particularly dangerous given the widespread deployment of these server versions in enterprise environments. The exploitability of this vulnerability is enhanced by the fact that it can be triggered through standard HTTP requests without requiring authentication, making it an attractive target for automated scanning and exploitation campaigns. Organizations running these affected versions face significant risk of unauthorized access, data breaches, and potential complete system compromise.
Mitigation strategies for CVE-2002-0147 should prioritize immediate patching of affected systems through Microsoft security updates, as the vendor released specific fixes for this vulnerability. Network administrators should implement defensive measures including firewall rules to restrict access to vulnerable IIS servers and monitor for suspicious HTTP traffic patterns that may indicate exploitation attempts. The implementation of web application firewalls and intrusion detection systems can provide additional layers of protection by identifying and blocking malformed chunked encoding requests. Organizations should also consider disabling ASP functionality on IIS servers where it is not strictly required, reducing the attack surface for potential exploitation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving remote code execution and privilege escalation, and defensive strategies should align with mitigations for these threat categories. System administrators should conduct thorough vulnerability assessments to identify all affected systems and implement comprehensive monitoring solutions to detect exploitation attempts, while also ensuring that backup and recovery procedures are in place to address potential compromise scenarios.