CVE-1999-1362 in Windows
Summary
by MITRE
Win32k.sys in Windows NT 4.0 before SP2 allows local users to cause a denial of service (crash) by calling certain WIN32K functions with incorrect parameters.
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Analysis
by VulDB Data Team • 04/20/2026
The vulnerability identified as CVE-1999-1362 represents a critical flaw in the Windows NT 4.0 operating system's kernel-mode driver component known as win32k.sys. This driver serves as the core interface between user-mode applications and the Windows graphical subsystem, managing window management, graphics rendering, and user interface operations. The vulnerability specifically affects systems running Windows NT 4.0 prior to Service Pack 2, making it particularly significant given the widespread deployment of this operating system in enterprise environments during the late 1990s. The flaw exists within the kernel-level function handling mechanisms that process user requests for graphical operations, creating a pathway for malicious or unintended parameter manipulation that can compromise system stability.
The technical nature of this vulnerability stems from inadequate parameter validation within the win32k.sys driver implementation. When local users invoke specific WIN32K functions with malformed or incorrect parameters, the driver fails to properly validate input data before processing it, leading to memory corruption conditions. This type of vulnerability falls under the CWE-125 vulnerability category, which encompasses out-of-bounds reads and writes that can occur when programs access memory locations outside the intended bounds of allocated buffers. The improper parameter handling creates a condition where the kernel becomes susceptible to crashes, as the driver's internal state becomes corrupted when processing invalid input sequences. The vulnerability specifically targets the kernel-mode execution context where the driver operates with elevated privileges, making the potential impact significantly more severe than typical user-mode flaws.
The operational impact of this vulnerability extends beyond simple system instability, as it provides local attackers with a reliable method for causing system-wide denial of service conditions. Since the vulnerability operates at the kernel level within win32k.sys, successful exploitation results in immediate system crashes and potential system reboots, disrupting business operations and user productivity. In enterprise environments where Windows NT 4.0 systems were commonly deployed for server and desktop roles, this vulnerability could lead to significant operational downtime and service disruption. The local nature of the attack means that any user with access to the system could potentially trigger the vulnerability, making it particularly dangerous in multi-user environments where privilege escalation might not be required. This flaw also demonstrates the critical importance of kernel-level security validation, as the impact of such vulnerabilities can completely compromise system availability and stability.
Mitigation strategies for CVE-1999-1362 primarily focus on applying the appropriate Microsoft security patches and service packs that address the underlying parameter validation issues in the win32k.sys driver. Organizations should prioritize immediate deployment of Windows NT 4.0 Service Pack 2 or later versions that contain the necessary fixes for this vulnerability. System administrators should also consider implementing additional monitoring and logging mechanisms to detect potential exploitation attempts, particularly focusing on unusual patterns of kernel function calls. The vulnerability highlights the broader ATT&CK technique of privilege escalation through kernel-mode exploitation, making it important for security teams to maintain comprehensive visibility into kernel-level activities and function calls. Additionally, organizations should conduct thorough vulnerability assessments to identify systems running unpatched Windows NT 4.0 installations and ensure proper network segmentation to limit potential attack vectors. The remediation process should also include regular security updates and patch management procedures to prevent similar vulnerabilities from being introduced in future system configurations.