CVE-2013-4154 in libvirt
Summary
by MITRE
The qemuAgentCommand function in libvirt before 1.1.1, when a guest agent is not configured, allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via vectors related to "agent based cpu (un)plug," as demonstrated by the "virsh vcpucount foobar --guest" command.
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Analysis
by VulDB Data Team • 08/21/2017
The vulnerability identified as CVE-2013-4154 represents a critical denial of service flaw within the libvirt virtualization management library affecting versions prior to 1.1.1. This issue manifests when the qemuAgentCommand function processes guest agent related operations without proper null pointer validation, creating a condition where remote attackers can trigger system instability through carefully crafted commands. The vulnerability specifically impacts systems utilizing libvirt for managing virtual machines, where guest agents are not properly configured or available. The attack vector is particularly concerning as it leverages the virsh command interface, which is commonly used by system administrators and automated tools for virtual machine management operations.
The technical exploitation of this vulnerability occurs through the manipulation of agent based cpu plug/unplug operations within the libvirt framework. When a guest agent is not configured, the qemuAgentCommand function fails to properly validate null pointers during the processing of cpu count operations. This results in a NULL pointer dereference that causes the libvirt daemon to crash and terminate unexpectedly. The specific command pattern "virsh vcpucount foobar --guest" demonstrates how an attacker can leverage the guest cpu counting functionality to trigger the underlying memory access violation. This flaw aligns with CWE-476 which categorizes NULL pointer dereference vulnerabilities, and represents a classic example of improper input validation in virtualization management software.
The operational impact of CVE-2013-4154 extends beyond simple service disruption to potentially compromise entire virtualization environments. When the libvirt daemon crashes due to this vulnerability, it affects all virtual machine management operations handled by that daemon, potentially causing multiple virtual machines to become unmanageable or lose their connection to the hypervisor. This vulnerability particularly affects enterprise environments where libvirt is used extensively for managing large-scale virtualized infrastructures, as a successful attack could lead to significant operational downtime and potential data loss. The remote nature of the attack means that unauthorized users can exploit this flaw without requiring local access to the system, making it particularly dangerous in multi-tenant or cloud computing environments where isolation between users is critical.
Mitigation strategies for this vulnerability should focus on immediate version upgrades to libvirt 1.1.1 or later, which contain the necessary patches to address the NULL pointer dereference issue. Organizations should also implement network segmentation and access controls to limit exposure of libvirt management interfaces to trusted networks only. The vulnerability demonstrates the importance of proper input validation and error handling in virtualization management software, aligning with ATT&CK technique T1499.001 which covers network denial of service attacks. System administrators should also consider implementing monitoring solutions to detect unusual patterns of virsh command execution that might indicate exploitation attempts, and establish regular patching schedules to ensure all virtualization management components remain up-to-date with security fixes.