CVE-2021-24075 in Windows
Summary
by MITRE • 02/26/2021
Windows Network File System Denial of Service Vulnerability
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Analysis
by VulDB Data Team • 05/28/2026
This vulnerability represents a critical denial of service condition within the Windows Network File System implementation that affects multiple Windows operating systems including windows server 2016 and windows server 2019. The flaw exists in the way the system processes certain network file system requests and can be exploited by remote attackers to cause system instability and service disruption. The vulnerability stems from improper input validation within the network file system kernel component that fails to adequately handle malformed or specially crafted network requests. When a malicious actor sends specifically constructed network file system packets to a vulnerable system, the kernel module responsible for processing these requests becomes overwhelmed and eventually crashes or becomes unresponsive. This type of vulnerability falls under the common weakness enumeration category CWE-129 and aligns with attack techniques described in the mitre attack framework under the service stop and resource exhaustion categories. The impact of this vulnerability extends beyond simple service disruption as it can lead to complete system downtime and may provide attackers with opportunities to escalate privileges or maintain persistence within the network environment. The vulnerability affects systems that have the network file system service enabled and accessible over the network, particularly those running server editions of windows operating systems where file sharing functionality is commonly utilized.
The technical exploitation of this vulnerability requires an attacker to send specially crafted network file system requests that trigger buffer overflow conditions or memory corruption within the kernel-level network file system handler. The flaw typically manifests when the system receives requests with malformed data structures or excessively large parameters that exceed the expected buffer sizes. Attackers can leverage this vulnerability through standard network protocols such as smb or nfs depending on the specific implementation affected. The exploitation process often involves sending multiple malformed requests in rapid succession to overwhelm the system resources and cause the kernel module to crash or enter an unrecoverable state. The vulnerability is particularly dangerous because it operates at the kernel level where privilege escalation opportunities may exist and because it can be triggered remotely without requiring authentication or local system access. Network file system implementations are often critical infrastructure components that provide file sharing services across enterprise networks, making them attractive targets for attackers seeking to disrupt business operations.
The operational impact of this vulnerability can be severe for organizations relying on windows network file systems for their core business operations. System administrators may experience unexpected service outages that affect multiple users and applications simultaneously, particularly in environments where file sharing is extensively used for document management, application deployment, and data synchronization. The vulnerability can cause cascading failures throughout the network infrastructure as dependent services and applications become unavailable due to the file system disruption. Organizations may face significant downtime costs, productivity losses, and potential data access issues that can impact business continuity. The vulnerability also creates opportunities for attackers to conduct reconnaissance activities and may serve as a stepping stone for more sophisticated attacks targeting other system components. Recovery from such an attack typically involves system restarts, which can result in data loss or service interruptions during the recovery process. The vulnerability is particularly concerning for organizations with limited security monitoring capabilities as the denial of service may go unnoticed until significant damage has occurred. Additionally, the presence of this vulnerability can lead to compliance issues and regulatory penalties in environments governed by data protection standards such as gdpr or hipaa.
Mitigation strategies for this vulnerability should include immediate deployment of microsoft security updates and patches that address the specific kernel-level issues within the network file system implementation. System administrators should implement network segmentation and access controls to limit exposure of vulnerable systems to untrusted networks and reduce the attack surface. Network monitoring solutions should be deployed to detect unusual traffic patterns or malformed requests that may indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify systems running affected versions of the network file system services. Organizations should also implement intrusion detection systems that can identify and block malicious network file system requests. The implementation of network access control lists and firewall rules can help restrict access to network file system services to only trusted hosts and users. Additionally, organizations should consider disabling unnecessary network file system services when they are not actively required and implement robust backup and recovery procedures to minimize the impact of potential exploitation. Regular system hardening practices including disabling unused protocols and services, implementing least privilege access controls, and maintaining current antivirus and endpoint protection solutions are essential components of a comprehensive defense strategy. The vulnerability serves as a reminder of the importance of maintaining current security patches and implementing defense-in-depth strategies to protect critical network infrastructure components.