CVE-2013-4153 in libvirt
Summary
by MITRE
Double free vulnerability in the qemuAgentGetVCPUs function in qemu/qemu_agent.c in libvirt 1.0.6 through 1.1.0 allows remote attackers to cause a denial of service (daemon crash) via a cpu count request, as demonstrated by the "virsh vcpucount dom --guest" command.
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Analysis
by VulDB Data Team • 05/07/2018
The CVE-2013-4153 vulnerability represents a critical double free error within the libvirt virtualization management library, specifically affecting versions 1.0.6 through 1.1.0. This flaw exists in the qemuAgentGetVCPUs function located in qemu/qemu_agent.c, where improper memory management leads to a denial of service condition that can crash the libvirt daemon. The vulnerability is particularly concerning as it allows remote attackers to exploit this condition through legitimate management commands, making it a significant threat to virtualization infrastructure integrity. The attack vector is triggered when a malicious user executes the "virsh vcpucount dom --guest" command against a targeted domain, which causes the daemon to attempt to free the same memory block twice.
The technical implementation of this double free vulnerability stems from inadequate memory handling within the qemu agent communication layer of libvirt. When processing guest CPU count requests, the qemuAgentGetVCPUs function fails to properly track memory allocations and deallocations, resulting in the same memory pointer being passed to free() twice. This fundamental flaw in memory management violates standard security practices and creates a predictable crash condition that can be reliably exploited. The vulnerability aligns with CWE-415, which specifically addresses double free conditions in memory management, and represents a classic example of improper resource management that can lead to arbitrary code execution or system instability. The flaw occurs because the function does not properly validate memory allocation states or maintain proper reference counting during the processing of virtual CPU information requests.
The operational impact of this vulnerability extends beyond simple daemon crashes, as it can severely disrupt virtualization environments by causing cascading failures in hypervisor management. When the libvirt daemon crashes due to this double free condition, all virtual machines managed by that daemon may become inaccessible or unstable, potentially leading to service disruption for multiple tenants in cloud or enterprise virtualization deployments. Attackers can leverage this vulnerability to perform persistent denial of service attacks against virtualization infrastructure, making it particularly dangerous in multi-tenant environments where such disruptions can affect numerous users or applications simultaneously. The vulnerability's remote exploitability means that unauthorized users can trigger the condition without requiring local system access, making it an attractive target for attackers seeking to compromise virtualization platforms.
Mitigation strategies for CVE-2013-4153 focus on immediate version upgrades to libvirt 1.1.1 or later, where the double free condition has been resolved through proper memory management implementation. System administrators should prioritize patching affected libvirt installations and monitor for any continued exploitation attempts. Additionally, implementing network segmentation and access controls around libvirt management interfaces can help reduce the attack surface, while regular security audits of virtualization infrastructure should include checks for similar memory management flaws. The fix typically involves proper memory allocation tracking and ensuring that freed memory pointers are set to NULL to prevent subsequent reuse, aligning with ATT&CK technique T1489 which covers disruption of services through resource exhaustion or corruption. Organizations should also consider implementing intrusion detection systems to monitor for exploitation attempts of known virtualization vulnerabilities and maintain comprehensive backup and recovery procedures to minimize impact from such attacks.