CVE-2017-9310 in QEMU
Summary
by MITRE
QEMU (aka Quick Emulator), when built with the e1000e NIC emulation support, allows local guest OS privileged users to cause a denial of service (infinite loop) via vectors related to setting the initial receive / transmit descriptor head (TDH/RDH) outside the allocated descriptor buffer.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2017-9310 affects QEMU virtualization software when configured with e1000e network interface controller emulation support. This represents a critical security flaw that can be exploited by privileged users within a guest operating system to disrupt the normal operation of virtual machines. The issue stems from inadequate validation of receive and transmit descriptor head values during network packet processing within the emulated network hardware. When maliciously crafted descriptor head values are set outside the bounds of allocated descriptor buffers, the virtual network interface enters an infinite loop condition that consumes excessive system resources and renders the virtual machine unresponsive to legitimate network operations.
The technical root cause of this vulnerability lies in the improper bounds checking mechanism within the e1000e network controller emulation code. Specifically, the TDH (Transmit Descriptor Head) and RDH (Receive Descriptor Head) registers control the positioning of packet processing within allocated descriptor rings. When these registers are manipulated to point beyond the allocated memory regions, the emulated network controller fails to properly validate these values before entering the packet processing loop. This flaw allows attackers to manipulate the descriptor head pointers in such a way that they create circular references within the descriptor ring, leading to an infinite loop in the packet processing routine. The vulnerability is classified under CWE-129 Input Validation and is categorized as a Denial of Service condition that affects the availability of virtual machine resources. From an operational perspective, this vulnerability represents a significant risk to virtualized environments where guest operating systems may have elevated privileges, as it can be exploited to disrupt services without requiring special privileges beyond those already granted to the guest system.
The operational impact of CVE-2017-9310 extends beyond simple service disruption, as it can be leveraged to create persistent resource exhaustion conditions that affect the entire virtualization host. Attackers can exploit this vulnerability to consume CPU cycles indefinitely, potentially leading to resource starvation for other virtual machines running on the same physical host. This makes the vulnerability particularly dangerous in multi-tenant environments where isolation between virtual machines is paramount. The attack vector requires only local access within the guest operating system and privileged user access, making it easily exploitable in scenarios where guest users have elevated privileges or where privilege escalation occurs through other means. The vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service and demonstrates how virtualization platforms can become attack vectors when insufficient input validation is implemented in emulated hardware components. Organizations running QEMU virtualization environments with e1000e network controller support should prioritize patching this vulnerability to prevent potential exploitation that could lead to system-wide availability issues and compromise the integrity of virtualized computing environments.
Mitigation strategies for CVE-2017-9310 should focus on immediate patch application from QEMU maintainers, which typically involves implementing proper bounds checking for descriptor head register values and ensuring that the emulated network controller validates all pointer positions against allocated buffer boundaries. System administrators should also consider disabling e1000e network controller support in virtual machines where this functionality is not strictly required, particularly in environments where guest operating systems may not be fully trusted. Additional protective measures include implementing network monitoring to detect unusual CPU utilization patterns that may indicate exploitation attempts, and conducting regular vulnerability assessments of virtualization environments to identify similar issues in other emulated hardware components. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of privilege escalation within guest operating systems, as the vulnerability requires only local access and privileged execution within the guest environment to be exploited effectively.