CVE-1999-1452 in Windows
Summary
by MITRE
GINA in Windows NT 4.0 allows attackers with physical access to display a portion of the clipboard of the user who has locked the workstation by pasting (CTRL-V) the contents into the username prompt.
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Analysis
by VulDB Data Team • 04/20/2026
The vulnerability described in CVE-1999-1452 represents a significant security flaw in the Windows NT 4.0 graphical identification and authentication (GINA) subsystem that fundamentally undermines the security model of workstation locking mechanisms. This weakness specifically targets the authentication process that occurs when a user locks their workstation, creating an unexpected information disclosure channel that can be exploited by attackers who have gained physical access to the system.
The technical flaw resides in how the GINA component handles clipboard contents during the authentication process, particularly when the system is in a locked state. When a user locks their workstation, the system should maintain a secure state where sensitive information remains protected from unauthorized access. However, this vulnerability allows an attacker with physical access to manipulate the clipboard contents and then paste them into the username prompt field of the login screen. The system's failure to properly sanitize or validate clipboard data during this specific authentication phase creates an attack vector where previously copied information can be exposed and potentially leveraged for further exploitation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the integrity of the workstation locking mechanism that users rely upon for security. An attacker can exploit this weakness to gain insights into the user's recent activities, potentially accessing sensitive data such as passwords, personal information, or business-critical details that were previously copied to the clipboard. This vulnerability is particularly concerning because it operates without requiring network access or elevated privileges, making it accessible to anyone with physical access to the machine. The attack requires only basic physical access and knowledge of the clipboard manipulation technique, making it a low-effort, high-impact exploit that can be carried out by adversaries with minimal technical expertise.
From a cybersecurity perspective, this vulnerability aligns with CWE-200, which addresses "Information Exposure," and demonstrates how improper handling of system components during authentication can create unexpected security gaps. The issue also relates to ATT&CK technique T1551.001, "Credentials in Files," as it enables attackers to extract potentially sensitive information from clipboard contents that may have contained credentials or other confidential data. Organizations implementing Windows NT 4.0 systems would have been particularly vulnerable to this attack vector, as the operating system lacked proper input validation and sanitization mechanisms to prevent clipboard content injection during the authentication process.
Mitigation strategies for this vulnerability would have required system administrators to implement strict physical security controls, including restricting unauthorized access to workstations and educating users about the risks of copying sensitive information to the clipboard. Additionally, the vulnerability highlighted the need for more robust authentication subsystem design and proper input validation during critical security operations. Microsoft's subsequent releases addressed this issue through improved GINA implementations and enhanced clipboard security mechanisms, but the vulnerability serves as a critical reminder of how seemingly minor implementation flaws in security-critical components can create substantial risks. The incident also underscored the importance of considering all attack vectors, including physical access scenarios, when designing security systems and demonstrated how user behavior and system interaction patterns could be exploited to bypass intended security controls.