CVE-2016-9908 in QEMU
Summary
by MITRE
Quick Emulator (Qemu) 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' 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 • 07/15/2019
The vulnerability identified as CVE-2016-9908 affects Quick Emulator Qemu when configured with Virtio GPU Device emulator support, representing a critical information disclosure weakness that undermines the fundamental isolation principles of virtualization environments. This flaw exists within the command processing mechanism of the Virtio GPU device implementation, specifically during handling of the VIRTIO_GPU_CMD_GET_CAPSET command which is designed to retrieve capabilities information from the graphics device. The vulnerability stems from inadequate memory boundary checking and improper validation of input parameters during command execution, allowing unauthorized access to host system memory contents.
The technical implementation of this vulnerability resides in the Virtio GPU device emulation layer where the GET_CAPSET command processing does not properly validate the size parameter or memory allocation boundaries before copying data from guest-controlled buffers to host memory structures. This misconfiguration creates a memory access pattern that enables a malicious guest user or process to manipulate the command parameters in such a way that the device emulator reads beyond intended memory boundaries, effectively leaking host memory contents including potentially sensitive data such as kernel memory, guest memory mappings, or other confidential information. The flaw operates through a classic buffer over-read condition where the emulator fails to enforce proper memory access controls between guest and host environments, directly violating the security boundaries that virtualization platforms are designed to maintain.
From an operational perspective, this vulnerability presents a severe threat to virtualized environments as it allows a compromised guest operating system to extract arbitrary host memory contents, potentially exposing kernel data structures, credential information, or other sensitive system resources. The impact extends beyond simple information leakage since the leaked memory contents could contain cryptographic keys, passwords, or other confidential data that could be leveraged for further attacks. Attackers could potentially use this vulnerability to escalate privileges, bypass security controls, or perform advanced persistent threat activities by analyzing the leaked memory for exploitable patterns. The vulnerability is particularly dangerous in multi-tenant cloud environments where guest isolation is paramount, as it could enable one tenant to access another tenant's memory contents or system resources.
Mitigation strategies for CVE-2016-9908 should prioritize immediate patching of affected Qemu versions with the vendor-provided security updates that address the memory boundary validation issues in the Virtio GPU command processing. Organizations should also implement network segmentation and access controls to limit guest user privileges and reduce the attack surface. Additional defensive measures include disabling unnecessary Virtio GPU device features when not required, implementing memory monitoring solutions to detect unusual memory access patterns, and conducting regular security assessments of virtualization environments. The vulnerability aligns with CWE-125 Uncontrolled Memory Access and represents a violation of the principle of least privilege as defined in cybersecurity frameworks, while also mapping to ATT&CK technique T1055 Process Injection and T1082 System Information Discovery, as attackers could leverage this information leakage for further reconnaissance and exploitation activities.