CVE-2000-0167 in IIS
Summary
by MITRE
IIS Inetinfo.exe allows local users to cause a denial of service by creating a mail file with a long name and a .txt.eml extension in the pickup directory.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 02/16/2025
The vulnerability identified as CVE-2000-0167 represents a classic denial of service flaw affecting Microsoft Internet Information Services version 5.0 and earlier installations. This weakness specifically targets the inetinfo.exe process responsible for managing IIS web server operations and mail services. The vulnerability exploits a fundamental flaw in how the system handles mail file processing within the pickup directory, which serves as the primary location where incoming mail messages are temporarily stored before being processed by the mail service. The attack vector leverages the creation of specially crafted mail files with extended filenames that exceed normal processing limits, ultimately causing the mail service to become unresponsive or crash entirely.
The technical implementation of this vulnerability stems from inadequate input validation and boundary checking within the mail file processing routines. When a local user creates a mail file with a filename exceeding predetermined length limits and appends the .txt.eml extension, the system's mail service becomes overwhelmed during the parsing and validation phases. The inetinfo.exe process fails to properly handle these extended filenames, leading to buffer overflows or memory corruption conditions that result in service termination. This flaw operates at the system level rather than through network protocols, making it particularly dangerous as it requires only local system access to exploit. The vulnerability demonstrates characteristics consistent with CWE-121, which describes buffer overflow conditions where insufficient boundary checking allows for memory corruption, and aligns with ATT&CK technique T1499.100, focusing on denial of service through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire server availability and reliability. Organizations running affected IIS versions may experience complete mail service outages, preventing legitimate email communication and potentially disrupting business operations that depend on email infrastructure. The local privilege requirement means that attackers do not need network access or external exploitation tools, making this vulnerability particularly concerning for environments where local access might be compromised. System administrators face challenges in detecting and mitigating this issue since it occurs during normal mail processing operations, potentially masking the attack within legitimate system activity. The vulnerability affects not only email delivery but also the overall stability of the web server platform, as the mail service component shares system resources and memory spaces with other IIS services.
Mitigation strategies for this vulnerability focus on both immediate defensive measures and long-term system hardening approaches. The most effective immediate solution involves applying Microsoft security patches and updates specifically designed to address this buffer overflow condition in the mail processing component. System administrators should implement strict file naming conventions and length restrictions within the pickup directory to prevent the creation of excessively long filenames. Network segmentation and access control measures can limit local system access to reduce exploitation potential. Additionally, implementing monitoring solutions that track unusual file creation patterns in mail directories can help detect potential exploitation attempts. Organizations should consider implementing automated alerting systems that monitor for service disruptions in mail processing components, as these disruptions often precede complete service failures. The vulnerability also underscores the importance of regular security assessments and patch management programs to prevent similar issues from arising in other system components. This case study exemplifies how seemingly minor input validation flaws can result in significant operational disruptions and emphasizes the critical need for comprehensive security testing throughout the software development lifecycle.