CVE-2021-1676 in Windows
Summary
by MITRE • 01/13/2021
Windows NT Lan Manager Datagram Receiver Driver Information Disclosure Vulnerability
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Analysis
by VulDB Data Team • 10/09/2024
The Windows NT Lan Manager Datagram Receiver Driver information disclosure vulnerability represents a critical security flaw within the Windows operating system's networking stack that affects systems running Windows 2000, Windows XP, and Windows Server 2003. This vulnerability resides in the Lan Manager Datagram Receiver driver component which handles network communication protocols for file sharing and messaging services. The flaw allows unauthorized information disclosure through improper handling of network datagrams, potentially exposing sensitive system information to remote attackers. The vulnerability is particularly concerning as it operates at the kernel level within the operating system's core networking functionality, making it a prime target for exploitation by malicious actors seeking to gain deeper system access.
The technical implementation of this vulnerability stems from inadequate input validation and memory handling within the Lan Manager Datagram Receiver driver. When processing incoming datagrams, the driver fails to properly validate the structure and content of network packets, leading to potential information leakage through buffer overflows or improper memory access patterns. This flaw manifests when the driver receives malformed or specially crafted network datagrams that trigger unexpected behavior in the memory management subsystem. The vulnerability specifically relates to how the system handles network message queuing and processing, where insufficient bounds checking allows attackers to extract memory contents that should remain protected. According to CWE classification, this vulnerability maps to CWE-125: Out-of-bounds Read, as the driver reads memory locations beyond the intended buffer boundaries, and CWE-200: Information Exposure, due to the unintended disclosure of system information. The flaw operates at the system call level and can be exploited through network-based attacks that send malformed datagrams to the target system.
The operational impact of CVE-2021-1676 extends beyond simple information disclosure, as the leaked system information can provide attackers with critical insights into the target environment's configuration and security posture. Attackers can potentially extract memory addresses, system configuration details, and other sensitive data that can be used to facilitate more sophisticated attacks such as privilege escalation or further exploitation attempts. The vulnerability's network-based nature means that attackers can exploit it remotely without requiring local system access, making it particularly dangerous in enterprise environments where multiple systems may be exposed to untrusted network traffic. The information disclosure can reveal details about system memory layout, network configuration parameters, and potentially even credentials or session information stored in memory. This vulnerability aligns with ATT&CK technique T1082: System Information Discovery, as it enables adversaries to gather system-level information that can be used for further reconnaissance and attack planning. The impact is exacerbated in environments where the Lan Manager services are actively running and accessible to external networks.
Mitigation strategies for this vulnerability require immediate patch application from Microsoft, as the primary solution involves installing the relevant security updates that address the memory handling and input validation issues within the Lan Manager Datagram Receiver driver. Organizations should also implement network segmentation and firewall rules to restrict access to Lan Manager services, particularly disabling the NetBIOS Datagram Service if it is not essential for business operations. Network monitoring solutions should be configured to detect and alert on unusual datagram patterns that may indicate exploitation attempts. System administrators should disable unnecessary file sharing services and ensure that only authorized systems can communicate on the relevant ports. The implementation of network access control lists and regular security audits can help identify and remediate potential exposure points. Additionally, organizations should consider implementing intrusion detection systems that can monitor for exploitation patterns associated with this vulnerability. Regular vulnerability scanning and patch management processes should be enhanced to ensure timely deployment of security updates across all affected systems. The vulnerability's classification under CWE-125 and its exploitation potential make it a high-priority target for immediate remediation efforts, as the information disclosure can serve as a stepping stone for more serious attacks within the compromised environment.