CVE-2001-1518 in Windows
Summary
by MITRE
RunAs (runas.exe) in Windows 2000 only creates one session instance at a time, which allows local users to cause a denial of service (RunAs hang) by creating a named pipe session with the authentication server without any request for service. NOTE: the vendor disputes this vulnerability, however the vendor also presents a scenario in which other users could be affected if running on a Terminal Server. Therefore this is a vulnerability.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability described in CVE-2001-1518 affects the RunAs utility in Windows 2000 systems, specifically targeting the session management mechanism that controls how authentication occurs for elevated privilege operations. This issue stems from the design limitation where runas.exe maintains only a single active session instance at any given time, creating a fundamental architectural constraint that can be exploited for denial of service attacks. The vulnerability manifests when local users leverage the named pipe session creation functionality to establish connections with the authentication server without actually requesting any service, effectively monopolizing the authentication session and preventing other legitimate authentication requests from completing successfully.
The technical flaw resides in the session handling logic of the RunAs utility which does not properly manage concurrent session instances or implement appropriate timeout mechanisms for idle authentication connections. When a malicious user creates a named pipe session without requesting any actual service, the authentication server maintains this connection in a waiting state indefinitely, consuming system resources and blocking subsequent authentication attempts. This behavior creates a race condition where legitimate users attempting to perform elevated operations through RunAs find their requests hanging or failing to complete, as the system cannot process additional authentication requests while the malicious session remains active. The vulnerability specifically leverages the Windows named pipe communication mechanism to establish persistent connections that remain in an uninitialized state, exploiting the single-session limitation of the RunAs implementation.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise system availability and user productivity in environments where RunAs functionality is frequently utilized for administrative tasks. In terminal server environments, the risk is amplified as multiple concurrent users may be affected simultaneously, creating cascading failures where legitimate administrative operations become impossible to perform. The vendor's position that this is not a vulnerability appears to stem from the assumption that local users with the ability to create named pipe sessions would already possess sufficient privileges to cause more significant damage, but this perspective fails to account for the indirect impact on system availability and the potential for exploitation by users with limited privileges who can still disrupt service for other legitimate users. The vulnerability demonstrates a classic case of insufficient resource management in authentication systems where connection state is not properly tracked or timed out.
Mitigation strategies for this vulnerability should focus on implementing proper session timeout mechanisms and resource cleanup procedures within the RunAs utility implementation. System administrators should consider restricting access to RunAs functionality to authorized users only, particularly in terminal server environments where multiple users share the same system resources. The implementation of monitoring solutions to detect and terminate idle named pipe sessions would provide an additional layer of protection against this type of exploitation. Organizations should also consider implementing network-level access controls to limit the ability of local users to create arbitrary named pipe connections to authentication services. This vulnerability aligns with CWE-470, which addresses the use of insecure random number generators, and relates to ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' through system design weaknesses. The issue highlights the importance of proper session management and resource cleanup in authentication systems and demonstrates how seemingly minor architectural limitations can create significant security implications in multi-user environments.