CVE-2014-9718 in QEMU
Summary
by MITRE
The (1) BMDMA and (2) AHCI HBA interfaces in the IDE functionality in QEMU 1.0 through 2.1.3 have multiple interpretations of a function's return value, which allows guest OS users to cause a host OS denial of service (memory consumption or infinite loop, and system crash) via a PRDT with zero complete sectors, related to the bmdma_prepare_buf and ahci_dma_prepare_buf functions.
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Analysis
by VulDB Data Team • 05/09/2022
The vulnerability identified as CVE-2014-9718 represents a critical denial of service weakness affecting QEMU virtualization environments from version 1.0 through 2.1.3. This issue manifests within the IDE functionality's BMDMA and AHCI HBA interfaces, specifically targeting how these components handle data transfer descriptors. The flaw arises from ambiguous interpretations of function return values during DMA buffer preparation operations, creating exploitable conditions that can be leveraged by malicious guest operating system users to compromise host system stability. The vulnerability operates through the bmdma_prepare_buf and ahci_dma_prepare_buf functions, which process Physical Region Descriptor Tables containing zero complete sectors, leading to unpredictable behavior in the host system's memory management and execution flow.
The technical exploitation of this vulnerability occurs when a guest OS presents a PRDT (Physical Region Descriptor Table) with zero complete sectors to the virtualized storage controller. This specific condition causes the bmdma_prepare_buf and ahci_dma_prepare_buf functions to interpret return values inconsistently, potentially leading to infinite loops or excessive memory consumption patterns within the QEMU process. The ambiguous return value handling creates a scenario where the host system's virtualization layer fails to properly validate or reject malformed DMA transfer requests, allowing malicious input to trigger resource exhaustion or execution path failures. The vulnerability's impact extends beyond simple resource consumption, as the inconsistent function return interpretation can cause system crashes or complete host system instability, making it particularly dangerous in production virtualization environments.
From an operational perspective, this vulnerability poses significant risks to virtualized infrastructure security and availability. Attackers with access to guest operating systems can exploit this weakness to consume excessive host memory resources or force the QEMU process into infinite execution loops, effectively causing denial of service for other virtual machines sharing the same host system. The vulnerability is particularly concerning because it requires no elevated privileges within the guest environment, making it accessible to any user with basic guest OS access. The impact extends to both memory exhaustion and system crash scenarios, with the potential for cascading failures in multi-tenant virtualization environments where multiple guests share the same physical host resources. Organizations running QEMU-based virtualization platforms in production environments face substantial risk of service disruption and potential data availability issues due to this vulnerability.
The mitigation strategy for CVE-2014-9718 involves immediate patching of QEMU installations to versions beyond 2.1.3, where the ambiguous return value interpretations have been resolved through improved input validation and consistent function return handling. System administrators should also implement monitoring for unusual memory consumption patterns or process hangs that might indicate exploitation attempts. Additionally, virtualization administrators can consider implementing guest OS restrictions and limiting guest access to potentially malicious storage operations. The vulnerability aligns with CWE-691, which addresses insufficient control of a resource through a control plane, and relates to ATT&CK technique T1499.001, which involves resource exhaustion attacks. Organizations should also consider implementing network segmentation and access controls to limit guest OS capabilities and reduce the attack surface available to potential exploiters of this vulnerability.