CVE-2013-4151 in QEMU
Summary
by MITRE
The virtio_load function in virtio/virtio.c in QEMU 1.x before 1.7.2 allows remote attackers to execute arbitrary code via a crafted savevm image, which triggers an out-of-bounds write.
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Analysis
by VulDB Data Team • 06/20/2021
The vulnerability identified as CVE-2013-4151 represents a critical security flaw in QEMU virtualization software that affects versions 1.x prior to 1.7.2. This issue resides within the virtio_load function located in the virtio/virtio.c file, which is a core component responsible for handling virtual device state loading during virtual machine save and restore operations. The vulnerability specifically targets the savevm functionality that allows virtual machines to be suspended and resumed at a later time, maintaining their complete state including memory contents, device states, and execution context. When a maliciously crafted savevm image is loaded into a vulnerable QEMU instance, the system becomes susceptible to arbitrary code execution, fundamentally compromising the security isolation that virtualization environments are designed to maintain.
The technical root cause of this vulnerability stems from inadequate input validation and bounds checking within the virtio_load function. During the process of loading a savevm image, the function processes serialized device state data without properly verifying the size or structure of the incoming data. This allows an attacker to craft a savevm image containing malicious data that exceeds the allocated buffer boundaries, resulting in an out-of-bounds write condition. The flaw occurs because the function assumes that the serialized data will conform to expected parameters, failing to validate the length of data structures or the overall size of the savevm image before processing. Such buffer overflow conditions create opportunities for attackers to overwrite adjacent memory locations, potentially corrupting critical data structures or injecting executable code into the virtual machine's execution context.
The operational impact of CVE-2013-4151 extends far beyond simple privilege escalation, as it fundamentally undermines the security model of virtualized environments. Attackers can leverage this vulnerability to execute arbitrary code within the context of the QEMU process, which typically runs with elevated privileges on the host system. This creates a potential attack vector where an unprivileged user could gain full control over the host machine, effectively breaking the isolation barrier between virtual machines and the underlying physical infrastructure. The vulnerability is particularly dangerous in multi-tenant cloud environments where multiple users share the same physical host, as it could enable one tenant to compromise another's virtual machines or even the host system itself. Additionally, since savevm functionality is commonly used in virtual machine management, backup operations, and live migration scenarios, this vulnerability could be exploited during routine administrative tasks, making it particularly insidious and difficult to detect.
The exploitation of this vulnerability aligns with several tactics and techniques documented in the ATT&CK framework, particularly those related to privilege escalation and execution within virtualized environments. The out-of-bounds write condition creates opportunities for memory corruption attacks that can be leveraged to achieve code execution, representing a classic exploit pattern that falls under the category of memory corruption vulnerabilities. From a CWE perspective, this vulnerability maps directly to CWE-121, which describes heap-based buffer overflow conditions, and CWE-787, which covers out-of-bounds write scenarios. The remediation approach requires careful input validation and bounds checking within the virtio_load function, including proper validation of savevm image structure and size constraints before any data processing occurs. System administrators should immediately upgrade to QEMU version 1.7.2 or later, which includes patches that address the buffer overflow conditions and implement proper input validation mechanisms. Additional mitigations include implementing strict access controls on savevm operations, monitoring for unusual savevm file creation or loading activities, and employing virtualization security solutions that can detect and prevent such exploitation attempts. Organizations should also consider implementing network segmentation and access controls to limit exposure of QEMU instances to untrusted users or networks, as the vulnerability requires remote exploitation capabilities to be effectively leveraged against target systems.