CVE-2016-2841 in QEMU
Summary
by MITRE
The ne2000_receive function in the NE2000 NIC emulation support (hw/net/ne2000.c) in QEMU before 2.5.1 allows local guest OS administrators to cause a denial of service (infinite loop and QEMU process crash) via crafted values for the PSTART and PSTOP registers, involving ring buffer control.
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Analysis
by VulDB Data Team • 08/24/2022
The vulnerability identified as CVE-2016-2841 resides within the NE2000 network interface card emulation implementation in QEMU hypervisor software. This flaw specifically affects versions prior to 2.5.1 and manifests in the ne2000_receive function located in the hw/net/ne2000.c file. The issue represents a critical security concern that can be exploited by local administrators within guest operating systems to disrupt the normal operation of virtualized environments. The vulnerability stems from inadequate validation of register values within the network card emulation layer, creating a potential pathway for malicious actors to compromise system availability.
The technical implementation of this vulnerability involves the manipulation of two specific registers within the NE2000 emulation: PSTART and PSTOP. These registers control the ring buffer management system that handles network packet transmission and reception within the virtualized network interface. When crafted values are written to these registers, the emulation logic fails to properly validate the boundary conditions and buffer limits, leading to a scenario where the receive function enters an infinite loop. This occurs because the ring buffer control mechanism becomes corrupted, causing the system to continuously process invalid buffer references without proper termination conditions. The flaw operates at the hardware emulation level, where the virtualized network card fails to properly handle edge cases in its buffer management algorithms, resulting in deterministic system failure.
The operational impact of this vulnerability extends beyond simple denial of service, as it can lead to complete system crashes and potential data loss within virtualized environments. Local guest administrators with access to the virtual machine can exploit this vulnerability to cause the QEMU process to crash, effectively terminating the virtual machine's network functionality and potentially disrupting other services running on the same host system. This type of attack represents a significant threat to cloud computing environments and virtualized infrastructures where multiple guest operating systems share the same physical hardware resources. The infinite loop condition can consume excessive CPU cycles and memory resources, potentially leading to resource exhaustion attacks that affect the overall performance and stability of the hosting environment.
Mitigation strategies for this vulnerability require immediate patching of QEMU installations to version 2.5.1 or later, which contains the necessary fixes for the register validation logic. System administrators should also implement monitoring solutions to detect unusual patterns in network card register access that might indicate exploitation attempts. The fix implemented in the patched versions involves enhanced input validation for the PSTART and PSTOP register values, ensuring that boundary conditions are properly checked before buffer operations are initiated. This vulnerability aligns with CWE-129, which addresses insufficient input validation, and represents a classic example of how hardware emulation flaws can create security risks in virtualization platforms. Organizations should also consider implementing network segmentation and access controls to limit local administrator privileges within guest operating systems, reducing the attack surface for such exploitation scenarios. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service techniques, as it allows local users to gain elevated impact through system-level disruptions.