CVE-2013-4541 in QEMU
Summary
by MITRE
The usb_device_post_load function in hw/usb/bus.c in QEMU before 1.7.2 might allow remote attackers to execute arbitrary code via a crafted savevm image, related to a negative setup_len or setup_index value.
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Analysis
by VulDB Data Team • 06/19/2021
The vulnerability identified as CVE-2013-4541 represents a critical code execution flaw within the QEMU virtualization platform that affects versions prior to 1.7.2. This issue resides in the usb_device_post_load function located in the hw/usb/bus.c file, which handles the restoration of USB device states during virtual machine save/restore operations. The vulnerability arises from insufficient input validation when processing savevm images, creating a potential attack vector for remote adversaries who can craft malicious save state files to exploit this weakness.
The technical root cause of this vulnerability stems from improper handling of setup_len and setup_index values within the USB device state restoration process. When QEMU encounters a crafted savevm image containing negative values for these parameters, the system fails to properly validate the input data before proceeding with memory operations. This validation gap enables attackers to manipulate the USB device state restoration logic, potentially leading to buffer overflows or arbitrary code execution within the QEMU process. The vulnerability is particularly dangerous because it occurs during the virtual machine state restoration phase, which is a critical operational point where the hypervisor processes untrusted data from external sources.
The operational impact of CVE-2013-4541 extends beyond simple privilege escalation, as it allows remote attackers to gain full control over the host system running vulnerable QEMU instances. Attackers can exploit this vulnerability by creating malicious savevm images containing crafted negative setup_len or setup_index values, which when loaded by a vulnerable QEMU instance can result in arbitrary code execution with the privileges of the QEMU process. This represents a severe security risk for cloud environments and virtualization platforms where multiple tenants share the same infrastructure, as a compromised virtual machine could potentially be used to attack the underlying host system. The vulnerability is classified under CWE-129 as "Improper Validation of Array Index" and aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Python" in scenarios where attackers might leverage compromised virtual environments to establish persistent access.
Mitigation strategies for this vulnerability require immediate patching of QEMU installations to version 1.7.2 or later, which implements proper input validation for USB device state restoration parameters. Organizations should also implement network segmentation and access controls to limit exposure to potentially malicious savevm images, while monitoring for suspicious virtual machine state file operations. The fix addresses the core issue by validating that setup_len and setup_index values remain within acceptable bounds before processing, preventing the exploitation of negative values that could lead to memory corruption. Additionally, system administrators should consider implementing virtual machine state file integrity checks and restrict the ability to load external save files to trusted sources only, as this vulnerability demonstrates the critical importance of validating all external data inputs in virtualization environments.