CVE-2017-5579 in QEMU
Summary
by MITRE
Memory leak in the serial_exit_core function in hw/char/serial.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-2017-5579 represents a critical memory management flaw within the QEMU virtualization platform that affects the serial character device implementation. This issue manifests in the serial_exit_core function located in the hw/char/serial.c source file, where improper memory deallocation during device unplug operations creates a persistent memory leak condition. The vulnerability specifically targets local guest operating system users who possess privileged access within the virtualized environment, enabling them to exploit this weakness through repeated device unplug operations that accumulate memory consumption on the host system.
The technical nature of this vulnerability stems from inadequate memory cleanup procedures during the serial device removal process. When guest users perform multiple device unplug operations, the serial_exit_core function fails to properly release allocated memory resources, resulting in progressive memory consumption that eventually leads to host system resource exhaustion. This memory leak directly impacts the QEMU process stability, causing it to consume excessive host memory until system performance degrades significantly or the process crashes entirely. The flaw operates at the hypervisor level where guest-to-host communication occurs, making it particularly dangerous as it can be exploited by malicious users within the guest environment to disrupt host operations.
From an operational perspective, this vulnerability creates a significant denial of service risk that can compromise the stability of virtualized environments. Attackers with guest privileges can systematically consume host memory resources through repeated device unplug operations, potentially leading to complete system instability or service interruption. The impact extends beyond simple resource exhaustion as it can affect other virtual machines running on the same host, creating cascading failures that compromise overall virtualization infrastructure reliability. This vulnerability particularly affects systems where QEMU serves as the primary virtualization backend and where guest users have elevated privileges or access to serial device management functions.
The vulnerability aligns with CWE-401, which categorizes memory leaks as a common weakness in software design, and demonstrates characteristics consistent with ATT&CK technique T1499.001, which covers network denial of service attacks through resource exhaustion. Mitigation strategies should include immediate patching of QEMU installations to address the memory deallocation issue in the serial_exit_core function, implementing resource monitoring and limiting guest access to device management operations, and establishing memory consumption thresholds to detect and prevent excessive resource usage. Additionally, system administrators should consider implementing virtual machine resource limits and isolation measures to contain the impact of such exploits. The vulnerability underscores the importance of proper memory management in hypervisor components and highlights the need for comprehensive security testing of virtualization platforms to prevent guest-to-host privilege escalation attacks that can compromise entire virtualization infrastructures.