CVE-2017-5526 in QEMU
Summary
by MITRE
Memory leak in hw/audio/es1370.c in QEMU (aka Quick Emulator) allows local guest OS privileged users to cause a denial of service (host memory consumption and QEMU process crash) via a large number of device unplug operations.
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Analysis
by VulDB Data Team • 09/08/2020
The vulnerability identified as CVE-2017-5526 represents a critical memory management flaw within the QEMU virtualization platform that specifically affects the ES1370 audio device emulation component. This issue resides in the hw/audio/es1370.c file and demonstrates how improper resource cleanup during device lifecycle operations can lead to significant system instability. The ES1370 audio controller is a legacy sound card emulation that was widely used in virtualized environments, making this vulnerability particularly concerning given the prevalence of such configurations in enterprise and cloud computing deployments.
The technical flaw manifests as a memory leak that occurs when the virtual audio device undergoes multiple unplug operations from the guest operating system. When a privileged user within the guest OS initiates numerous device unplug sequences, the QEMU hypervisor fails to properly release allocated memory resources associated with the ES1370 audio device. This memory leak accumulates over time, causing progressive host memory consumption that eventually leads to system instability. The vulnerability operates at the hypervisor level where guest OS users can exploit this weakness through legitimate device management operations, making it a particularly dangerous privilege escalation vector. The flaw aligns with CWE-401, which specifically addresses improper release of memory resources, and demonstrates how virtualization platforms can become vulnerable to resource exhaustion attacks when device management operations lack proper memory cleanup mechanisms.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise entire virtualized environments. As guest users repeatedly unplug and replug the ES1370 audio device, the host system experiences progressive memory consumption that can eventually cause the QEMU process to crash entirely. This behavior creates a scenario where malicious or compromised guest operating systems can systematically consume host resources, leading to service degradation or complete system outages. The vulnerability particularly affects environments where multiple virtual machines share host resources, as the memory consumption can cascade across multiple VMs and impact overall system performance. From an attack perspective, this vulnerability maps to ATT&CK technique T1499.001, which covers resource exhaustion attacks, and demonstrates how virtualization platforms can be targeted through legitimate guest operations to achieve denial of service conditions.
Mitigation strategies for CVE-2017-5526 should focus on both immediate patching and operational hardening measures. The primary solution involves applying the official QEMU patch that addresses the memory leak in the ES1370 audio device emulation code, which typically includes proper memory cleanup routines during device unplug operations. Organizations should also implement monitoring solutions to detect unusual patterns of device unplug operations that might indicate exploitation attempts. Virtualization administrators should consider disabling unnecessary audio device emulations in production environments where such features are not required, reducing the attack surface. Additionally, implementing resource limits and memory constraints on virtual machines can help contain the impact of memory leaks, preventing a single compromised VM from consuming excessive host resources. The vulnerability highlights the importance of thorough testing of device lifecycle operations in virtualization platforms and demonstrates why proper memory management practices are critical in hypervisor code, particularly in components that handle user-initiated device operations.