CVE-2015-7295 in QEMU
Summary
by MITRE
hw/virtio/virtio.c in the Virtual Network Device (virtio-net) support in QEMU, when big or mergeable receive buffers are not supported, allows remote attackers to cause a denial of service (guest network consumption) via a flood of jumbo frames on the (1) tuntap or (2) macvtap interface.
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Analysis
by VulDB Data Team • 06/26/2022
The vulnerability identified as CVE-2015-7295 resides within the QEMU virtualization platform's implementation of the virtio network device driver, specifically in the hw/virtio/virtio.c file. This flaw manifests when the virtual network interface operates without support for big or mergeable receive buffers, creating a critical pathway for denial of service attacks that can severely impact guest network performance. The vulnerability affects QEMU's handling of network traffic through both tuntap and macvtap interface implementations, which are commonly used for virtual machine network connectivity in cloud and virtualized environments.
The technical exploitation of this vulnerability occurs through a carefully crafted flood of jumbo frames transmitted to the guest operating system via the affected network interfaces. When the virtio-net driver encounters these large packets without proper buffer handling capabilities, it fails to process them efficiently, leading to resource exhaustion and subsequent network consumption issues within the guest environment. The flaw stems from inadequate buffer management logic that does not properly account for packet sizes exceeding standard network frame limits, particularly when the system lacks support for advanced buffer features like big buffers or mergeable buffers that would normally handle such traffic gracefully.
From an operational perspective, this vulnerability presents significant risks to virtualized environments where multiple guest operating systems share the same host infrastructure. Attackers can exploit this weakness to disrupt network services within target virtual machines, potentially causing complete network paralysis or severe performance degradation that affects business-critical applications. The impact extends beyond simple service disruption as it can be leveraged as a vector for more sophisticated attacks targeting virtualized infrastructure, particularly in cloud computing environments where resource exhaustion attacks can cascade across multiple tenants. The vulnerability's exploitation requires minimal resources and can be automated, making it particularly dangerous in environments with limited monitoring capabilities.
The root cause of this vulnerability aligns with CWE-129 Input Validation and CWE-400 Uncontrolled Resource Consumption weaknesses, where the system fails to properly validate packet sizes and manage buffer resources during network processing. This flaw also maps to ATT&CK technique T1499.004 for Network Denial of Service and T1566.001 for Phishing with Malicious Attachments, as it enables attackers to disrupt network services through crafted network traffic. Organizations utilizing QEMU-based virtualization platforms should prioritize immediate patching of affected systems, as the vulnerability can be exploited remotely without authentication requirements. Mitigation strategies include enabling support for big and mergeable receive buffers in virtio-net configurations, implementing network traffic monitoring to detect unusual jumbo frame patterns, and establishing proper network segmentation to limit the impact of potential exploitation attempts. Additionally, virtualization administrators should consider implementing rate limiting mechanisms on network interfaces and regularly review QEMU configuration settings to ensure optimal buffer management capabilities are enabled.