CVE-1999-0496 in Windows
Summary
by MITRE
A Windows NT 4.0 user can gain administrative rights by forcing NtOpenProcessToken to succeed regardless of the user's permissions, aka GetAdmin.
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Analysis
by VulDB Data Team • 04/16/2026
This vulnerability represents a critical privilege escalation flaw in Windows NT 4.0 that allows local users to obtain administrative privileges through manipulation of the NtOpenProcessToken API call. The issue stems from improper access control validation within the Windows security subsystem where the system fails to properly verify user permissions before granting access to process tokens. This weakness enables an attacker to bypass normal security boundaries and escalate their privileges to the highest administrative level within the operating system.
The technical implementation of this vulnerability exploits a flaw in the Windows security model where the NtOpenProcessToken function does not adequately validate whether the calling process has sufficient privileges to access another process's security token. When a user-level process attempts to open a token belonging to a higher-privileged process, the system should enforce strict access controls. However, due to the implementation flaw, the function can be forced to succeed regardless of the user's actual permissions, effectively allowing any local user to obtain administrative rights. This represents a classic case of insufficient privilege checking that violates fundamental security principles.
The operational impact of this vulnerability is severe as it provides local attackers with complete system control without requiring any special privileges or external exploitation vectors. Once exploited, the attacker gains full administrative rights including the ability to modify system files, install malicious software, create new user accounts, and access all system resources. The vulnerability affects all versions of Windows NT 4.0 and demonstrates a fundamental breakdown in the operating system's access control mechanisms. From an attacker's perspective, this represents a low-effort, high-impact privilege escalation method that can be reliably exploited on vulnerable systems.
This vulnerability aligns with CWE-266, which describes improper privilege management, and maps to ATT&CK technique T1068, privilege escalation through local exploitation. The flaw represents a direct violation of the principle of least privilege and demonstrates how improper access control implementation can lead to complete system compromise. Organizations running Windows NT 4.0 systems should immediately implement mitigations including applying available security patches, disabling unnecessary services, implementing strong access controls, and monitoring for suspicious process token access patterns. Additionally, system administrators should consider migrating to supported operating systems that have proper privilege validation mechanisms in place. The vulnerability highlights the critical importance of proper access control implementation and demonstrates why legacy systems require careful security management and eventual retirement from production environments.