CVE-2016-5338 in QEMU
Summary
by MITRE
The (1) esp_reg_read and (2) esp_reg_write functions in hw/scsi/esp.c in QEMU allow local guest OS administrators to cause a denial of service (QEMU process crash) or execute arbitrary code on the QEMU host via vectors related to the information transfer buffer.
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Analysis
by VulDB Data Team • 08/23/2022
The vulnerability identified as CVE-2016-5338 resides within the QEMU virtualization platform's SCSI emulation layer, specifically in the hardware scsi/esp.c file. This issue affects the esp_reg_read and esp_reg_write functions that handle register operations for the ESP (Enhanced SCSI Processor) controller implementation. The flaw represents a critical security weakness that can be exploited by local guest OS administrators who possess administrative privileges within the virtual machine environment. The vulnerability stems from inadequate input validation and buffer management within the SCSI command processing pipeline, creating opportunities for malicious code execution or system instability.
The technical implementation of this vulnerability involves improper handling of information transfer buffers during SCSI register operations. When guest operating systems execute specific SCSI commands through the ESP controller, the vulnerable functions fail to properly validate buffer boundaries and memory access patterns. This allows attackers to craft malicious SCSI commands that can manipulate memory locations within the QEMU process address space. The flaw enables attackers to either trigger memory corruption that results in QEMU process crashes or to inject and execute arbitrary code with the privileges of the QEMU host process. This represents a privilege escalation scenario where guest-level administrative access can be leveraged to achieve host-level code execution, potentially compromising the entire virtualization environment.
The operational impact of CVE-2016-5338 extends beyond simple denial of service conditions to encompass full system compromise within virtualized environments. Attackers can exploit this vulnerability to gain unauthorized access to host resources, potentially leading to data breaches, system compromise, or further attacks against other virtual machines sharing the same host infrastructure. The vulnerability affects all QEMU installations that utilize the ESP SCSI controller emulation, making it particularly dangerous in cloud computing and virtualization environments where multiple tenants share underlying hardware resources. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059 for command and scripting interpreter usage and T1068 for exploit for privilege escalation, while the underlying flaw maps to CWE-121 for heap-based buffer overflow and CWE-787 for out-of-bounds write conditions.
Mitigation strategies for CVE-2016-5338 should focus on both immediate patching and architectural defenses. Organizations must apply the official QEMU security patches released by the project maintainers to address the buffer handling issues in the esp.c file. Additionally, implementing virtual machine isolation measures through proper memory management and access controls can limit the potential impact of exploitation attempts. Network segmentation and monitoring solutions should be deployed to detect anomalous SCSI command sequences that might indicate exploitation attempts. System administrators should also consider implementing privilege separation mechanisms and limiting guest OS administrative capabilities where possible. The vulnerability demonstrates the importance of input validation in virtualization components and highlights the need for comprehensive security testing of hypervisor and emulator code to prevent similar issues in other virtualization subsystems.