CVE-2011-1872 in Windows
Summary
by MITRE
Hyper-V in Microsoft Windows Server 2008 Gold, SP2, R2, and R2 SP1 allows guest OS users to cause a denial of service (host OS infinite loop) via malformed machine instructions in a VMBus packet, aka "VMBus Persistent DoS Vulnerability."
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Analysis
by VulDB Data Team • 01/13/2025
The CVE-2011-1872 vulnerability represents a critical denial of service flaw within Microsoft Hyper-V virtualization platform affecting Windows Server 2008 and its subsequent service packs. This vulnerability specifically targets the VMBus communication mechanism that facilitates interaction between guest operating systems and the host Hyper-V hypervisor. The flaw arises from insufficient input validation within the VMBus packet processing subsystem, where malformed machine instructions can trigger an infinite loop condition in the host operating system. The vulnerability is particularly dangerous because it allows unprivileged guest OS users to execute code that can cause the host system to become unresponsive, effectively creating a persistent denial of service condition that can only be resolved through manual host reboot.
The technical implementation of this vulnerability leverages the VMBus protocol's handling of malformed packets that contain invalid machine instructions designed to exploit a specific processing loop within the Hyper-V kernel components. When the host hypervisor attempts to process these malformed VMBus packets, it enters an infinite loop during instruction decoding and execution phases, consuming all available CPU resources and rendering the host system incapable of processing legitimate requests. This behavior aligns with CWE-835, which describes the weakness of infinite loops or infinite recursion in software systems, and demonstrates how improper validation of external inputs can lead to critical system instability. The vulnerability specifically affects the VMBus packet processing code path, where the host hypervisor fails to properly validate the instruction set contained within VMBus packets before executing them.
The operational impact of this vulnerability extends beyond simple service disruption to create a significant security risk for virtualized environments. Attackers can exploit this vulnerability to create persistent denial of service conditions that can affect multiple virtual machines running on the same host system. The infinite loop condition can cause the host system to become completely unresponsive, requiring manual intervention to restore service. This vulnerability is particularly concerning in enterprise environments where virtualization is extensively used, as it can lead to cascading failures affecting multiple services and applications. The attack vector requires only guest OS privileges, making it accessible to any user with access to a virtual machine running on the affected Hyper-V host, which aligns with ATT&CK technique T1499.004 for network denial of service attacks.
Mitigation strategies for CVE-2011-1872 primarily involve applying the relevant Microsoft security updates and patches that address the VMBus packet validation issues. Organizations should ensure that all Windows Server 2008 systems running Hyper-V are updated with the latest security patches, particularly those released in response to this vulnerability. Additionally, implementing network segmentation and access controls to limit guest OS privileges can help reduce the attack surface. System administrators should also consider implementing monitoring solutions that can detect unusual CPU utilization patterns that may indicate the exploitation of this vulnerability. The vulnerability demonstrates the importance of proper input validation and robust error handling in hypervisor code, and serves as a reminder of the critical security considerations when developing virtualization platforms. Microsoft's security advisory for this vulnerability specifically recommends immediate patch deployment and provides detailed guidance on verifying the effectiveness of the applied patches.