CVE-2017-8379 in QEMU
Summary
by MITRE
Memory leak in the keyboard input event handlers support in QEMU (aka Quick Emulator) allows local guest OS privileged users to cause a denial of service (host memory consumption) by rapidly generating large keyboard events.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-8379 represents a critical memory management flaw within QEMU's keyboard input event handling subsystem that enables local privilege escalation and resource exhaustion attacks. This issue resides in the virtualization layer where guest operating systems can manipulate the hypervisor's memory allocation patterns through crafted keyboard input sequences, creating a persistent memory leak condition that gradually consumes host system resources. The vulnerability specifically affects QEMU versions prior to 2.10.0 and demonstrates how virtualization environments can be exploited to compromise system stability through seemingly benign input handling mechanisms.
The technical root cause of this vulnerability stems from inadequate memory management within the keyboard input event processing code path in QEMU's virtual input device implementation. When the guest OS generates keyboard events, the hypervisor fails to properly release memory allocated for event buffering and processing, leading to progressive memory consumption that can eventually exhaust available host resources. This memory leak occurs specifically during the handling of rapid keyboard event sequences where the input handler does not properly clean up allocated memory structures after processing each event, creating a cumulative effect that grows over time with repeated input generation. The flaw manifests as a failure to implement proper memory deallocation routines in the keyboard event processing pipeline, which is classified as a memory leak vulnerability under CWE-401.
The operational impact of this vulnerability extends beyond simple denial of service conditions to create potential system instability and performance degradation across virtualized environments. Local privileged users within the guest OS can exploit this weakness by generating high-frequency keyboard events that rapidly consume host memory, potentially leading to system crashes or complete resource exhaustion that affects other virtual machines running on the same host. This attack vector is particularly concerning in multi-tenant environments where one compromised guest system could potentially impact the entire host infrastructure. The vulnerability can be exploited through automated scripts that generate sustained keyboard event streams, making it difficult to detect and mitigate without proper monitoring of memory consumption patterns in virtualized environments.
Mitigation strategies for CVE-2017-8379 should focus on immediate software updates and implementation of host-level monitoring systems to detect abnormal memory consumption patterns. The most effective solution involves upgrading QEMU to version 2.10.0 or later where the memory leak has been addressed through proper memory deallocation mechanisms in the keyboard input event handlers. System administrators should also implement resource limits and monitoring for virtual machine memory usage to detect potential exploitation attempts. Additionally, the vulnerability aligns with ATT&CK technique T1499.001 which covers resource exhaustion attacks, and demonstrates how hypervisor-level vulnerabilities can be leveraged to create persistent denial of service conditions that affect the underlying infrastructure. Organizations should consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities in their virtualized environments, while also maintaining regular vulnerability assessments to identify similar memory management flaws in other virtualization components.