CVE-2016-4441 in QEMU
Summary
by MITRE
The get_cmd function in hw/scsi/esp.c in the 53C9X Fast SCSI Controller (FSC) support in QEMU does not properly check DMA length, which allows local guest OS administrators to cause a denial of service (out-of-bounds write and QEMU process crash) via unspecified vectors, involving an SCSI command.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/21/2022
The vulnerability identified as CVE-2016-4441 resides within the QEMU virtualization platform's implementation of the 53C9X Fast SCSI Controller support, specifically in the hw/scsi/esp.c file. This flaw affects the get_cmd function which handles SCSI command processing for the FSC controller. The vulnerability manifests as a critical issue in the DMA length validation mechanism that governs how data is transferred between guest operating systems and the virtualized SCSI controller. When a guest OS administrator executes specific SCSI commands, the system fails to properly validate the DMA transfer length, creating a condition that can be exploited to trigger memory corruption within the QEMU process.
The technical implementation of this vulnerability stems from inadequate input validation within the SCSI command processing pipeline. The get_cmd function in the esp.c module does not sufficiently verify the length parameters associated with DMA operations, allowing malicious or malformed SCSI commands to specify invalid transfer lengths that exceed allocated memory boundaries. This particular flaw falls under the CWE-129 category of Improper Validation of Array Index, specifically manifesting as an out-of-bounds write condition that can be triggered through guest OS administrative actions. The vulnerability is classified as a local privilege escalation vector since it requires guest OS administrator privileges but does not need elevated system privileges to exploit.
The operational impact of CVE-2016-4441 represents a significant denial of service threat to virtualized environments. When exploited, the vulnerability causes QEMU processes to crash due to memory corruption, effectively terminating the virtual machine hosting the compromised guest OS. This disruption can be particularly damaging in production environments where virtualization platforms serve critical workloads, potentially leading to service interruptions and data availability issues. The attack vector specifically involves SCSI command execution, making it relevant to systems that utilize SCSI storage or networking protocols within virtualized environments, particularly those implementing the 53C9X Fast SCSI Controller emulation.
Mitigation strategies for CVE-2016-4441 should focus on implementing proper input validation and bounds checking within the QEMU SCSI controller implementation. System administrators should ensure that all QEMU instances are updated to versions containing patches that address the DMA length validation issue, as the vulnerability was resolved through proper bounds checking mechanisms in subsequent releases. Additionally, implementing network segmentation and access controls to limit guest OS administrator privileges can reduce the attack surface, though this represents a defensive measure rather than a direct fix. The vulnerability demonstrates the importance of proper memory management and input validation in virtualization platforms, aligning with ATT&CK technique T1068 which covers local privilege escalation through exploitation of system vulnerabilities. Organizations should also consider implementing monitoring solutions to detect unusual SCSI command patterns that might indicate exploitation attempts, as this type of vulnerability can potentially be leveraged in more sophisticated attack scenarios beyond simple denial of service.