CVE-1999-1234 in Windows
Summary
by MITRE
LSA (LSASS.EXE) in Windows NT 4.0 allows remote attackers to cause a denial of service via a NULL policy handle in a call to (1) SamrOpenDomain, (2) SamrEnumDomainUsers, and (3) SamrQueryDomainInfo.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-1234 represents a critical flaw in the Local Security Authority (LSA) component of Windows NT 4.0, specifically within the LSASS.EXE process that handles security functions. This vulnerability manifests as a remote denial of service condition that can be exploited by attackers without requiring authentication or elevated privileges. The flaw occurs when the LSA service receives malformed policy handles during specific Remote Procedure Call (RPC) operations, creating a scenario where legitimate system services become unavailable to users and administrators.
The technical implementation of this vulnerability involves three specific RPC functions within the Security Account Manager (SAM) interface that are designed to manage domain security information. When attackers send specially crafted RPC requests containing NULL policy handles to SamrOpenDomain, SamrEnumDomainUsers, and SamrQueryDomainInfo functions, the LSASS.EXE process fails to properly validate these inputs. This lack of proper input validation causes the system to crash or become unresponsive, effectively preventing legitimate authentication and authorization requests from being processed. The vulnerability is classified as a buffer overflow condition under CWE-121, specifically representing an improper input validation scenario that leads to system instability and denial of service.
From an operational perspective, this vulnerability poses significant risks to Windows NT 4.0 environments that rely on domain authentication and security services. The remote nature of the exploit means that attackers can potentially disrupt critical network services without requiring physical access or prior authentication credentials, making it particularly dangerous in enterprise environments where domain controllers are essential for system operations. The impact extends beyond simple service disruption as the LSASS.EXE process failure affects the entire security infrastructure of the Windows domain, potentially rendering systems inaccessible to legitimate users and administrators. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting system services.
The exploitation of this vulnerability demonstrates a fundamental flaw in the Windows NT 4.0 security architecture where insufficient input validation in core system services creates opportunities for attackers to cause system-wide disruptions. Organizations running Windows NT 4.0 systems should implement immediate mitigations including network segmentation to limit access to domain controllers, firewall rules to restrict RPC traffic, and application whitelisting to prevent unauthorized execution of malicious RPC requests. Microsoft addressed this vulnerability through security updates and recommended that organizations migrate away from the deprecated Windows NT 4.0 platform to more modern operating systems that have improved input validation and security hardening measures. The vulnerability serves as a historical example of how insufficient validation of user-supplied data in system services can create widespread availability issues that affect critical infrastructure components.