CVE-2001-0666 in Exchange
Summary
by MITRE
Outlook Web Access (OWA) in Microsoft Exchange 2000 allows an authenticated user to cause a denial of service (CPU consumption) via a malformed OWA request for a deeply nested folder within the user s mailbox.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/05/2025
Microsoft Exchange 2000 Outlook Web Access presents a significant denial of service vulnerability that affects authenticated users within the system. This weakness resides in how OWA processes folder structures and handles recursive directory traversal operations. The vulnerability manifests when a user submits a malformed request that targets a deeply nested folder structure within their mailbox, causing the system to consume excessive cpu resources during processing. The flaw represents a classic case of insufficient input validation and inadequate recursion handling within the web access interface. According to CWE-400, this vulnerability falls under the category of Uncontrolled Resource Consumption, specifically involving CPU usage. The attack vector requires authentication, meaning that only users with valid credentials can exploit this weakness, though it can be leveraged to disrupt service availability for legitimate users. The operational impact extends beyond simple resource exhaustion as the excessive cpu consumption can degrade system performance and potentially affect other services running on the same server. This vulnerability directly impacts the availability aspect of the CIA triad by creating conditions where authorized users may experience degraded service or complete unavailability of their email access. The flaw demonstrates poor error handling and lacks proper bounds checking mechanisms when processing deeply nested folder hierarchies. From an attacker perspective, this represents a low-privilege but high-impact vector since it requires minimal effort to exploit while potentially causing significant disruption. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through resource exhaustion. Organizations utilizing Exchange 2000 with OWA enabled face particular risk since the system lacks proper safeguards against malformed folder requests. The issue stems from inadequate sanitization of user inputs within the web interface, particularly when handling complex folder structures. This weakness can be exploited repeatedly to maintain sustained resource consumption, making it particularly dangerous in environments where continuous access is required. The vulnerability affects the overall system stability and can potentially cascade into broader service degradation across the email infrastructure. Mitigation strategies should include implementing request rate limiting, adding proper input validation for folder paths, and establishing recursion depth limits within the OWA processing logic. System administrators should also consider implementing monitoring solutions to detect unusual cpu consumption patterns that may indicate exploitation attempts. The vulnerability highlights the importance of proper resource management and input validation in web applications, particularly those handling user-generated folder structures. Organizations should prioritize updating to supported versions of Exchange that address this class of vulnerability, as Microsoft has since released patches and updates to resolve similar issues in newer versions of their email platform.