CVE-2016-2392 in QEMU
Summary
by MITRE
The is_rndis function in the USB Net device emulator (hw/usb/dev-network.c) in QEMU before 2.5.1 does not properly validate USB configuration descriptor objects, which allows local guest OS administrators to cause a denial of service (NULL pointer dereference and QEMU process crash) via vectors involving a remote NDIS control message packet.
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Analysis
by VulDB Data Team • 08/24/2022
The vulnerability identified as CVE-2016-2392 resides within the USB Net device emulator component of QEMU hypervisor software, specifically in the is_rndis function located in hw/usb/dev-network.c. This flaw represents a critical security issue that affects QEMU versions prior to 2.5.1, where the software fails to properly validate USB configuration descriptor objects during USB network device emulation. The vulnerability stems from inadequate input validation mechanisms that should have been implemented to ensure the integrity of USB communication protocols within virtualized environments. This weakness allows malicious actors with administrative privileges within the guest operating system to exploit the hypervisor's USB network device emulation layer.
The technical exploitation of this vulnerability occurs through a specific attack vector involving remote NDIS control message packets that manipulate the USB configuration descriptor objects. When a guest OS administrator crafts malicious USB control messages that bypass normal validation procedures, the is_rndis function fails to properly handle these malformed descriptors, leading to a NULL pointer dereference condition. This type of memory access violation directly causes the QEMU process to crash and terminate unexpectedly, effectively resulting in a denial of service condition that impacts the entire virtualized environment. The flaw demonstrates poor error handling practices and inadequate boundary checking within the USB protocol stack implementation, which aligns with CWE-476, specifically NULL Pointer Dereference, and CWE-122, which addresses buffer overflow conditions.
The operational impact of CVE-2016-2392 extends beyond simple service disruption, as it represents a significant threat to virtualized infrastructure stability and security. When exploited, this vulnerability allows local guest administrators to crash the QEMU hypervisor process, which can lead to complete system downtime for all virtual machines running on that host. This creates a serious risk for cloud service providers and enterprise environments where multiple virtual machines share the same hypervisor infrastructure, potentially enabling attackers to cause widespread service disruption. The vulnerability also falls under ATT&CK technique T1499, which covers network denial of service attacks, and T1068, which addresses local privilege escalation through exploitation of software vulnerabilities. The attack requires minimal privileges within the guest OS, making it particularly dangerous as it can be exploited by users who already have administrative access to virtual machines.
Mitigation strategies for CVE-2016-2392 primarily focus on upgrading to QEMU version 2.5.1 or later, which includes the necessary patches to properly validate USB configuration descriptors and prevent the NULL pointer dereference condition. System administrators should implement comprehensive patch management procedures to ensure all virtualization platforms are updated with the latest security fixes. Additional defensive measures include restricting guest OS administrative privileges where possible, implementing network segmentation to limit USB device access, and monitoring for unusual USB control message patterns that might indicate exploitation attempts. Organizations should also consider implementing hypervisor-level monitoring to detect process crashes and automatic restart procedures to minimize service disruption. The vulnerability highlights the importance of proper input validation and error handling in virtualization software, emphasizing that security controls must be implemented at multiple layers to protect against both external and internal threats.