CVE-2019-0723 in Windows
Summary
by MITRE
A denial of service vulnerability exists when Microsoft Hyper-V Network Switch on a host server fails to properly validate input from a privileged user on a guest operating system. An attacker who successfully exploited the vulnerability could cause the host server to crash. To exploit the vulnerability, an attacker who already has a privileged account on a guest operating system, running as a virtual machine, could run a specially crafted application that causes a host machine to crash. The update addresses the vulnerability by modifying how virtual machines access the Hyper-V Network Switch.
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Analysis
by VulDB Data Team • 02/20/2026
The vulnerability identified as CVE-2019-0723 represents a critical denial of service weakness within Microsoft Hyper-V's Network Switch implementation that fundamentally undermines the stability of virtualized environments. This flaw exists in the host server's validation mechanisms when processing input from guest operating systems, specifically targeting the Hyper-V Network Switch component that manages network traffic between virtual machines and physical network interfaces. The vulnerability demonstrates a classic privilege escalation pathway where a malicious actor with elevated privileges within a guest virtual machine can manipulate the host system's network infrastructure to cause system-wide crashes.
The technical exploitation of CVE-2019-0723 relies on a specific validation failure within the Hyper-V Network Switch's input handling processes, which falls under the weakness category of improper input validation as classified by CWE-20. Attackers must first establish a privileged account within a guest operating system to leverage this vulnerability, making it a sophisticated attack vector that requires initial compromise of a virtual machine. The exploitation mechanism involves executing a specially crafted application that targets the network switch's processing routines, causing memory corruption or resource exhaustion that ultimately leads to the host server crashing. This type of attack directly maps to the ATT&CK technique T1059.001 for command and scripting interpreter and T1499.004 for network denial of service, as it leverages virtualization platforms to achieve system disruption.
The operational impact of this vulnerability extends beyond simple service interruption, as it can compromise entire virtualized infrastructures where multiple virtual machines rely on the same host server for network connectivity. Organizations utilizing Hyper-V environments face significant risk of cascading failures when this vulnerability is exploited, potentially affecting dozens or hundreds of virtual machines simultaneously. The crash condition affects not only individual virtual machines but also the underlying host system's ability to maintain network services and potentially disrupt business continuity for applications that depend on virtualized networking. The vulnerability particularly impacts data center environments where Hyper-V is extensively used for server consolidation and virtual machine deployment.
Microsoft's remediation approach for CVE-2019-0723 involves modifying how virtual machines interact with the Hyper-V Network Switch, implementing enhanced input validation mechanisms and strengthening the boundary checks between guest and host network components. The fix addresses the root cause by introducing additional validation layers that prevent malicious input from causing the network switch to malfunction. Organizations should prioritize applying the security update immediately, as the vulnerability requires no special privileges beyond existing guest access, making it particularly dangerous in multi-tenant environments where guest isolation is critical. The mitigation strategy should include monitoring for anomalous network behavior that might indicate exploitation attempts and implementing additional network segmentation measures to limit the potential impact of any successful attacks. This vulnerability highlights the importance of maintaining strict isolation boundaries within virtualized environments and demonstrates the critical need for robust input validation in hypervisor components that serve as foundational infrastructure for enterprise computing environments.