CVE-2016-9907 in QEMU
Summary
by MITRE
Quick Emulator (Qemu) built with the USB redirector usb-guest support is vulnerable to a memory leakage flaw. It could occur while destroying the USB redirector in 'usbredir_handle_destroy'. A guest user/process could use this issue to leak host memory, resulting in DoS for a host.
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Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2016-9907 affects Quick Emulator QEMU when configured with USB redirector usb-guest support, representing a critical memory management flaw that undermines system stability and security. This issue manifests during the destruction phase of USB redirector functionality within the qemu process, specifically within the usbredir_handle_destroy function. The flaw enables malicious guest users or processes to exploit improper memory deallocation mechanisms, creating a pathway for unauthorized memory access and potential system compromise.
The technical implementation of this vulnerability stems from inadequate memory cleanup procedures within the usb-guest redirector component of QEMU. When the usbredir_handle_destroy function executes, it fails to properly release allocated memory resources, leading to memory leakage patterns that can be systematically exploited. This memory management failure creates a persistent resource drain that can accumulate over time, ultimately leading to denial of service conditions on the host system. The vulnerability specifically targets the USB redirection functionality that allows guest operating systems to access host USB devices through virtualized interfaces.
From an operational perspective, this vulnerability poses significant risks to virtualized environments where QEMU serves as the primary hypervisor. Attackers with access to guest systems can leverage this flaw to systematically consume host memory resources, potentially causing complete system crashes or rendering the host unresponsive to legitimate requests. The impact extends beyond simple resource exhaustion, as memory leakage can also affect system performance and stability, particularly in multi-tenant virtualization environments where multiple guests share the same host resources. This vulnerability directly relates to CWE-401, which addresses improper resource release or memory leaks in software systems.
The attack vector for this vulnerability requires a guest user or process to interact with USB redirection functionality, making it particularly concerning in environments where guest systems have elevated privileges or where users have the ability to establish USB connections. The memory leakage occurs during normal operation when USB devices are disconnected or when the USB redirector component is being torn down, making it difficult to detect and prevent through standard monitoring mechanisms. This vulnerability aligns with ATT&CK technique T1499.001, which covers resource exhaustion attacks targeting system memory, and represents a significant threat to virtualization security postures.
Mitigation strategies for CVE-2016-9907 should focus on immediate patching of QEMU installations with versions that address the memory deallocation issue in usbredir_handle_destroy. System administrators should also implement monitoring solutions to detect unusual memory consumption patterns that may indicate exploitation attempts. Additionally, limiting USB redirection capabilities for untrusted guests and implementing proper access controls can reduce the attack surface. The vulnerability highlights the importance of thorough memory management testing in virtualization components and demonstrates the critical need for maintaining up-to-date virtualization software to protect against known memory-related security flaws. Organizations should also consider implementing network segmentation and privilege separation to limit the potential impact of such vulnerabilities in their virtualized infrastructures.