CVE-2015-7512 in QEMU
Summary
by MITRE
Buffer overflow in the pcnet_receive function in hw/net/pcnet.c in QEMU, when a guest NIC has a larger MTU, allows remote attackers to cause a denial of service (guest OS crash) or execute arbitrary code via a large packet.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 07/02/2022
The vulnerability identified as CVE-2015-7512 represents a critical buffer overflow flaw within the QEMU virtualization environment that specifically affects the pcnet_receive function in the hw/net/pcnet.c module. This issue emerges when a guest operating system utilizes a network interface card with an MTU setting that exceeds the expected parameters, creating a scenario where maliciously crafted network packets can exploit the software's memory handling mechanisms. The vulnerability operates at the hypervisor level, making it particularly dangerous as it can potentially be leveraged by remote attackers to compromise the entire virtualization infrastructure.
The technical implementation of this vulnerability stems from inadequate bounds checking within the pcnet_receive function, which processes incoming network packets for the PCnet network adapter emulation. When a guest system configures its network interface with an MTU larger than what the QEMU implementation anticipates, the buffer allocated for packet reception becomes insufficient to accommodate the oversized data. This condition creates a classic buffer overflow scenario where excess data overflows into adjacent memory regions, potentially corrupting critical program state or allowing attackers to overwrite function pointers and control execution flow. The flaw manifests as a direct result of CWE-121, which categorizes buffer overflow conditions where insufficient bounds checking allows memory to be overwritten.
The operational impact of CVE-2015-7512 extends beyond simple denial of service conditions to encompass potential arbitrary code execution capabilities that could enable attackers to compromise guest operating systems or even the host system. Remote attackers can exploit this vulnerability by transmitting specially crafted network packets that exceed the expected MTU size, causing the guest OS to crash or potentially allowing code execution within the virtualized environment. This represents a significant threat to virtualized environments where multiple tenants share the same infrastructure, as successful exploitation could enable privilege escalation or lateral movement attacks. The vulnerability directly aligns with ATT&CK technique T1059, which covers command and control through the execution of malicious code in compromised systems.
Mitigation strategies for this vulnerability require immediate patching of QEMU installations to address the buffer overflow condition in the pcnet_receive function. System administrators should ensure that all virtualization environments are updated with the latest security patches from their respective vendors, as the fix typically involves implementing proper bounds checking and memory allocation validation before processing network packets. Additionally, network administrators should monitor for unusual network traffic patterns that might indicate exploitation attempts, and consider implementing network segmentation to limit the potential impact of successful attacks. Organizations should also review their virtualization policies to ensure that guest operating systems are configured with appropriate MTU settings that align with the hypervisor capabilities, reducing the attack surface for this specific vulnerability. The remediation process must also include comprehensive testing to ensure that network performance is not negatively impacted by the applied patches while maintaining the security posture of the virtualized infrastructure.