CVE-2001-0337 in IIS
Summary
by MITRE
The Microsoft MS01-014 and MS01-016 patches for IIS 5.0 and earlier introduce a memory leak which allows attackers to cause a denial of service via a series of requests.
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Analysis
by VulDB Data Team • 05/11/2019
The vulnerability described in CVE-2001-0337 represents a critical memory management flaw within Microsoft Internet Information Services version 5.0 and earlier systems. This issue emerged as part of the MS01-014 and MS01-016 security updates designed to address other vulnerabilities, but inadvertently introduced a significant weakness in the IIS memory handling mechanisms. The flaw specifically affects the web server's ability to properly manage memory allocation and deallocation during request processing, creating a condition where memory resources gradually become consumed without proper release.
The technical implementation of this vulnerability stems from improper memory management within the IIS web server's request processing pipeline. When multiple requests are processed in succession, particularly those involving certain HTTP methods or specific request parameters, the system fails to correctly free allocated memory blocks. This memory leak occurs in the context of how IIS handles concurrent connections and request processing, where each request consumes memory resources that should be released upon completion of processing. The flaw manifests as a progressive accumulation of memory usage that eventually leads to system resource exhaustion.
The operational impact of this vulnerability extends beyond simple resource consumption, creating a reliable denial of service condition that can be easily exploited by malicious actors. Attackers can systematically send a series of carefully crafted requests to the affected IIS server, causing memory consumption to increase steadily until the system becomes unresponsive or crashes entirely. This type of attack is particularly dangerous because it requires minimal technical expertise to execute and can effectively shut down web services without requiring advanced attack vectors or privileged access. The vulnerability affects the availability aspect of the system's security posture, making it a significant concern for organizations relying on IIS 5.0 or earlier versions for their web hosting infrastructure.
The memory leak vulnerability aligns with CWE-401, which specifically addresses improper management of dynamically allocated memory, and represents a classic example of resource exhaustion attacks that fall under the ATT&CK technique T1499.004 for Network Denial of Service. Organizations affected by this vulnerability face the risk of complete service disruption, potentially affecting multiple websites hosted on the same server, and may experience cascading failures if the server hosts critical business applications. The impact is particularly severe in environments where IIS serves as the primary web server platform and where system administrators have not implemented proper monitoring or mitigation strategies to detect the gradual memory consumption.
Mitigation strategies for this vulnerability require immediate patch application, as Microsoft released specific updates to address the memory leak issue introduced by the problematic patches. System administrators should also implement monitoring solutions to track memory usage patterns and establish automated alerts when memory consumption exceeds normal thresholds. Additionally, organizations should consider implementing rate limiting and connection throttling mechanisms to prevent single attackers from exhausting system resources through sustained request patterns. The vulnerability underscores the importance of thorough testing of security patches in production environments and highlights the need for robust incident response procedures to quickly identify and address resource exhaustion attacks.