CVE-2000-0663 in Windows
Summary
by MITRE
The registry entry for the Windows Shell executable (Explorer.exe) in Windows NT and Windows 2000 uses a relative path name, which allows local users to execute arbitrary commands by inserting a Trojan Horse named Explorer.exe into the %Systemdrive% directory, aka the "Relative Shell Path" vulnerability.
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Analysis
by VulDB Data Team • 10/13/2025
The CVE-2000-0663 vulnerability represents a critical privilege escalation flaw in Windows NT and Windows 2000 operating systems that stems from improper handling of the Windows Shell executable registry entry. This vulnerability specifically targets the Windows Shell component responsible for managing the graphical user interface and file explorer functionality. The issue manifests when the system attempts to launch the Explorer.exe process during system startup or user session initialization, creating a path traversal condition that can be exploited by local attackers.
The technical root cause of this vulnerability lies in the registry configuration where the Windows Shell executable path is defined using a relative path rather than an absolute path specification. This design flaw allows attackers to manipulate the system's execution flow by placing a malicious executable with the same name as the legitimate shell component in a strategic location. The vulnerability is classified under CWE-22 as a "Path Traversal" issue, where an attacker can manipulate the path resolution mechanism to execute unintended code. The Windows registry key responsible for defining the shell executable location contains a relative path that resolves to the system drive root directory, making it susceptible to manipulation through the %Systemdrive% environment variable.
The operational impact of this vulnerability is significant as it provides local attackers with a means to execute arbitrary code with the privileges of the targeted user account. When a user logs into the system, the Windows Shell automatically launches Explorer.exe, and due to the relative path configuration, the system will execute the first instance of Explorer.exe found in the search path. This creates an opportunity for attackers to place a malicious Trojan Horse executable in the %Systemdrive% directory, which will be executed instead of the legitimate system component. The vulnerability essentially allows for persistent code execution and can be leveraged to establish backdoors, escalate privileges, or perform other malicious activities within the compromised system environment.
The attack vector for this vulnerability is straightforward and requires only local system access, making it particularly dangerous in multi-user environments where attackers may have limited access to system resources. According to ATT&CK framework, this vulnerability maps to T1068 - "Exploitation for Privilege Escalation" and T1546.001 - "Registry Run Keys / Startup Folder" as the attack leverages the Windows registry to establish persistence. The vulnerability also relates to T1059 - "Command and Scripting Interpreter" since successful exploitation typically involves executing commands through the compromised shell component. The exploitation process does not require network connectivity or special privileges beyond local system access, making it accessible to a broad range of threat actors.
Mitigation strategies for CVE-2000-0663 involve implementing proper registry configuration practices and system hardening measures. Organizations should ensure that all registry entries defining system executables use absolute paths rather than relative paths to prevent path traversal attacks. The most effective remediation involves modifying the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell to specify the complete absolute path to the legitimate Explorer.exe executable located in the System32 directory. Additionally, implementing strong file system permissions and monitoring for unauthorized modifications to system directories can help detect potential exploitation attempts. System administrators should also apply the relevant security patches provided by Microsoft, which address this specific registry path configuration issue. Regular security audits of registry configurations and file system permissions can help identify and remediate similar vulnerabilities that may exist in other system components, ensuring comprehensive protection against path traversal attacks.