CVE-2001-1122 in Windows
Summary
by MITRE
Windows NT 4.0 SP 6a allows a local user with write access to winnt/system32 to cause a denial of service (crash in lsass.exe) by running the NT4ALL exploit program in SPECIAL mode.
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Analysis
by VulDB Data Team • 02/01/2025
The vulnerability described in CVE-2001-1122 represents a critical local privilege escalation flaw in Windows NT 4.0 Service Pack 6a that specifically targets the Local Security Authority Subsystem Service. This vulnerability operates through a carefully crafted exploit program known as NT4ALL that leverages the existing write permissions within the winnt/system32 directory to manipulate system components. The flaw stems from inadequate input validation and memory management within the lsass.exe process, which is responsible for enforcing local security policies and managing authentication operations. When executed with appropriate privileges, the exploit triggers a buffer overflow condition that ultimately results in a system crash, effectively causing a denial of service that renders the affected system unusable.
The technical implementation of this vulnerability involves exploiting the permissions model within Windows NT 4.0 where a local user with write access to the system32 directory can manipulate critical system files. The NT4ALL exploit program operates in SPECIAL mode to execute a specific sequence of operations that directly targets the lsass.exe process memory structures. This attack vector demonstrates a classic buffer overflow exploit pattern where the malicious program writes beyond allocated memory boundaries, causing the lsass.exe process to terminate unexpectedly. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, which occurs when insufficient bounds checking allows an attacker to overwrite adjacent memory locations. The exploit essentially corrupts the process execution context, leading to an unhandled exception that crashes the security subsystem.
The operational impact of CVE-2001-1122 extends beyond simple system unavailability as it represents a fundamental weakness in the Windows NT 4.0 security architecture. When lsass.exe crashes, the system loses its ability to perform authentication functions, effectively locking out legitimate users and preventing new authentication attempts. This denial of service condition can be particularly damaging in enterprise environments where Windows NT 4.0 servers serve as domain controllers or authentication points. The vulnerability exposes the underlying design flaw in how the security subsystem handles privilege escalation requests, making it a prime target for attackers seeking to disrupt network services. From an attack perspective, this vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation and T1499 which covers network denial of service attacks.
Mitigation strategies for this vulnerability require immediate implementation of the official Microsoft security patch that addresses the specific buffer overflow condition in lsass.exe. Organizations should ensure that all Windows NT 4.0 systems are updated to Service Pack 6a or later versions that contain the necessary security fixes. Access control measures must be implemented to restrict write permissions to the winnt/system32 directory, limiting potential exploit scenarios to only authorized personnel with legitimate system maintenance requirements. Additionally, system monitoring should be enhanced to detect unusual activity patterns in authentication services and process termination events that could indicate exploitation attempts. Network segmentation strategies should be employed to isolate critical authentication services, reducing the potential impact of successful exploitation. The vulnerability also underscores the importance of maintaining up-to-date security patches and implementing principle of least privilege access controls to prevent unauthorized modification of critical system components.