CVE-2002-0364 in IIS
Summary
by MITRE
Buffer overflow in the chunked encoding transfer mechanism in IIS 4.0 and 5.0 allows attackers to execute arbitrary code via the processing of HTR request sessions, aka "Heap Overrun in HTR Chunked Encoding Could Enable Web Server Compromise."
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Analysis
by VulDB Data Team • 09/19/2025
The vulnerability described in CVE-2002-0364 represents a critical buffer overflow flaw within the HTTP transfer encoding mechanism of Microsoft Internet Information Services versions 4.0 and 5.0. This security weakness specifically manifests during the processing of HTR (HTML Server) request sessions, where the web server's handling of chunked transfer encoding creates an exploitable heap overrun condition. The flaw resides in how IIS manages the memory allocation for processing HTTP chunks, particularly when dealing with specially crafted malicious requests that exceed the allocated buffer boundaries. This vulnerability operates at the core of the web server's request processing pipeline, making it a prime target for attackers seeking to compromise server systems.
The technical implementation of this vulnerability involves the manipulation of HTTP chunked transfer encoding headers within HTR request processing. When IIS receives a request containing malformed chunked encoding data, the server's internal buffer management fails to properly validate the data length against allocated memory space. This results in memory corruption that can be leveraged to overwrite adjacent memory locations, potentially allowing attackers to inject and execute arbitrary code with the privileges of the IIS service account. The heap overrun occurs during the parsing of chunked data streams where the server allocates memory for chunks without sufficient bounds checking, creating a predictable memory layout that attackers can exploit through carefully crafted payloads. The vulnerability specifically affects the HTTP protocol handling layer, making it particularly dangerous as it can be triggered through standard web traffic without requiring special authentication or access privileges.
The operational impact of this vulnerability extends far beyond simple denial of service scenarios, as it provides attackers with full system compromise capabilities. Successful exploitation can result in complete server takeover, enabling attackers to execute arbitrary commands, install backdoors, access sensitive data, and potentially use the compromised server as a launch point for further attacks within the network infrastructure. The vulnerability affects organizations running legacy IIS 4.0 and 5.0 systems, which were prevalent in enterprise environments during the early 2000s, making it a significant concern for organizations with outdated web server infrastructure. The exploitability of this vulnerability is enhanced by the fact that it operates at the HTTP protocol level, meaning that attackers can leverage standard web browser traffic or automated tools to deliver payloads, making detection and prevention more challenging. Additionally, the vulnerability's impact is amplified because IIS typically runs with elevated privileges, potentially allowing attackers to gain administrative access to the entire server environment.
Mitigation strategies for CVE-2002-0364 primarily focus on immediate system updates and architectural defenses. The most effective approach involves applying Microsoft security patches released in response to this vulnerability, which address the underlying buffer overflow in the chunked encoding implementation. Organizations should also implement network-level protections such as web application firewalls and intrusion detection systems that can identify and block malformed chunked encoding requests. Network segmentation and access controls should be implemented to limit exposure of vulnerable IIS systems, while monitoring systems should be deployed to detect anomalous HTTP traffic patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and maps to ATT&CK technique T1190 for exploitation of remote services, emphasizing the need for comprehensive defensive measures that address both the immediate vulnerability and broader attack surface considerations. Regular security assessments and vulnerability scanning should be conducted to ensure all legacy IIS systems are properly patched and that no vulnerable components remain operational within the network infrastructure.