CVE-2016-9912 in QEMU
Summary
by MITRE
Quick Emulator (Qemu) built with the Virtio GPU Device emulator support is vulnerable to a memory leakage issue. It could occur while destroying gpu resource object in 'virtio_gpu_resource_destroy'. A guest user/process could use this flaw to leak host memory bytes, resulting in DoS for a host.
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Analysis
by VulDB Data Team • 07/15/2019
The vulnerability identified as CVE-2016-9912 affects Quick Emulator QEMU when configured with Virtio GPU Device emulator support, representing a critical memory management flaw that enables guest-side attackers to exploit host system resources. This issue manifests during the destruction of GPU resource objects within the virtio_gpu_resource_destroy function, where insufficient memory cleanup mechanisms allow malicious guest processes to repeatedly allocate and retain host memory references. The flaw specifically targets the virtualized graphics subsystem that enables guest operating systems to utilize host GPU capabilities through Virtio device emulation, creating a pathway for unauthorized memory consumption that can escalate to complete system compromise.
The technical exploitation of this vulnerability occurs through the improper handling of GPU resource cleanup operations where the virtio_gpu_resource_destroy function fails to properly release all allocated host memory regions associated with GPU objects. When a guest user process triggers resource destruction operations, the emulator does not adequately verify or clean up all memory mappings, leading to gradual memory leakage that can consume significant portions of the host system's available memory. This memory leak behavior creates a predictable pattern that allows attackers to systematically exhaust host resources, ultimately resulting in denial of service conditions that can crash or render the host system unusable. The vulnerability is classified under CWE-401 as "Improper Release of Memory Before Removing Last Reference" and represents a classic case of resource management failure in virtualized environments.
The operational impact of CVE-2016-9912 extends beyond simple resource exhaustion, as it fundamentally compromises the stability and security of virtualized environments where QEMU serves as the primary hypervisor. Attackers can leverage this flaw to perform persistent resource consumption attacks that may go unnoticed for extended periods, gradually degrading host performance while maintaining operational stealth. The vulnerability affects systems running QEMU versions with Virtio GPU support enabled, particularly impacting cloud environments, virtual desktop infrastructures, and any deployment where guest operating systems require GPU acceleration capabilities. Organizations utilizing virtualization technologies for multi-tenant environments face heightened risk as this flaw can enable attackers to target not only individual virtual machines but potentially compromise the entire host infrastructure through memory exhaustion attacks.
Mitigation strategies for CVE-2016-9912 should prioritize immediate patching of affected QEMU versions to address the memory cleanup implementation in the virtio_gpu_resource_destroy function. System administrators must ensure that all virtualized environments are updated with the latest QEMU releases that contain proper memory management fixes for GPU resource handling. Additional protective measures include implementing strict resource limits and monitoring for unusual memory consumption patterns within virtual environments, as well as disabling Virtio GPU support where such functionality is not essential for guest operating systems. Organizations should also consider implementing network segmentation and access controls to limit guest user privileges and reduce the attack surface available to potential exploiters. The vulnerability demonstrates the critical importance of proper memory management in virtualized environments and aligns with ATT&CK technique T1499.001 for "Network Denial of Service" and T1059.001 for "Command and Scripting Interpreter" as attackers may leverage this flaw to establish persistent resource consumption patterns that can be used for broader system compromise.