CVE-2016-9845 in QEMU
Summary
by MITRE
QEMU (aka Quick Emulator) built with the Virtio GPU Device emulator support is vulnerable to an information leakage issue. It could occur while processing 'VIRTIO_GPU_CMD_GET_CAPSET_INFO' command. A guest user/process could use this flaw to leak contents of the host memory bytes.
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Analysis
by VulDB Data Team • 07/22/2019
The vulnerability identified as CVE-2016-9845 affects QEMU virtualization software when configured with Virtio GPU Device emulator support, representing a critical information disclosure flaw that undermines the fundamental security isolation between guest and host systems. This issue manifests specifically during processing of the VIRTIO_GPU_CMD_GET_CAPSET_INFO command, which is part of the Virtio GPU protocol used for graphics acceleration in virtualized environments. The flaw enables a malicious guest user or process to extract sensitive host memory contents through improper memory handling during command processing.
The technical root cause of this vulnerability lies in inadequate input validation and memory management within QEMU's Virtio GPU implementation. When the emulator processes the GET_CAPSET_INFO command, it fails to properly restrict memory access boundaries, allowing the guest operating system to potentially read arbitrary host memory locations. This represents a classic case of insufficient access control and memory protection mechanisms, aligning with CWE-200 (Information Exposure) and CWE-125 (Out-of-Bounds Read) categories. The vulnerability demonstrates a failure in the principle of least privilege where guest processes should not be able to access host memory directly through virtualized device interfaces.
From an operational perspective, this vulnerability creates a severe attack vector that allows privilege escalation from guest user level to host-level memory access, effectively breaking the isolation boundary that virtualization platforms are designed to maintain. An attacker with access to a guest system could potentially extract sensitive information such as cryptographic keys, passwords, or other confidential data stored in host memory. The impact extends beyond simple information leakage as it fundamentally compromises the security model of virtualized environments, making it easier for attackers to perform lateral movement and establish persistent access to the host system. This vulnerability directly relates to ATT&CK technique T1055 (Process Injection) and T1082 (System Information Discovery) through the exploitation of virtualization interfaces.
Mitigation strategies for CVE-2016-9845 primarily involve updating QEMU to versions that address the memory handling issues in the Virtio GPU implementation, typically through patches that implement proper bounds checking and memory access restrictions. System administrators should disable Virtio GPU support in QEMU configurations when it is not required for virtual machine functionality, as this reduces the attack surface. Additionally, implementing network segmentation and access controls to limit guest user privileges can help reduce the potential impact of such vulnerabilities. The vulnerability highlights the importance of proper input validation and memory management in virtualization software components, emphasizing the need for regular security updates and thorough testing of virtualization environments. Organizations should also consider implementing monitoring solutions to detect anomalous memory access patterns that could indicate exploitation attempts against similar virtualization vulnerabilities.