CVE-2017-9373 in QEMU
Summary
by MITRE
Memory leak in QEMU (aka Quick Emulator), when built with IDE AHCI Emulation support, allows local guest OS privileged users to cause a denial of service (memory consumption) by repeatedly hot-unplugging the AHCI device.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2017-9373 represents a critical memory management flaw within QEMU's implementation of IDE AHCI (Advanced Host Controller Interface) emulation. This issue specifically affects virtualized environments where QEMU serves as the hypervisor platform, creating a scenario where malicious or compromised guest operating systems can exploit a memory leak condition. The vulnerability manifests when the AHCI device is repeatedly hot-unplugged from the virtual machine, a common operation in dynamic virtual environments where devices are frequently added or removed during runtime operations.
The technical root cause of this vulnerability lies in the improper handling of memory allocation and deallocation within QEMU's AHCI emulation subsystem. When an AHCI device is hot-unplugged, the virtualization layer should properly release all associated memory resources and clean up internal data structures. However, due to flawed memory management logic, certain memory blocks remain allocated and unreferenced, creating a persistent memory leak that accumulates over repeated hot-unplug operations. This memory leak directly violates the principles of proper resource management and can be categorized under CWE-401, which specifically addresses improper handling of memory allocation and deallocation issues.
The operational impact of this vulnerability extends beyond simple resource consumption, as it enables a sophisticated denial of service attack that can severely compromise system stability and performance. Local guest OS privileged users, who typically have elevated privileges within the virtual machine environment, can exploit this vulnerability to systematically consume available memory resources on the host system. The cumulative nature of the memory leak means that repeated exploitation can eventually lead to complete memory exhaustion, causing the host system to become unresponsive or crash entirely. This vulnerability particularly affects virtualized environments where multiple guest operating systems share the same physical host resources, creating a potential attack vector that could impact the entire virtual infrastructure.
From an attack perspective, this vulnerability aligns with the ATT&CK framework's privilege escalation and resource exhaustion tactics, specifically targeting the system resources management domain. The attack requires minimal privileges within the guest OS, as it only necessitates the ability to perform hot-unplug operations on virtual devices, which are typically available to privileged users. The exploitability of this vulnerability demonstrates the importance of proper memory management in virtualization platforms, as the flaw exists at the hypervisor level where guest operating systems can directly influence host resource allocation. Organizations utilizing QEMU-based virtualization solutions must consider this vulnerability as a potential threat vector that could be exploited to compromise the availability of their virtualized infrastructure.
Mitigation strategies for this vulnerability should include immediate patch application from QEMU maintainers, which would address the memory leak in the AHCI emulation code. System administrators should also implement monitoring solutions to detect unusual memory consumption patterns that could indicate exploitation attempts. Additionally, virtualization platforms should consider implementing resource limits and quotas for guest operating systems to prevent a single compromised VM from consuming excessive host resources. The vulnerability highlights the critical need for comprehensive memory management testing in virtualization platforms and demonstrates the importance of proper resource cleanup procedures in complex software systems where guest and host environments interact dynamically.