CVE-2018-16867 in QEMU
Summary
by MITRE
A flaw was found in qemu Media Transfer Protocol (MTP) before version 3.1.0. A path traversal in the in usb_mtp_write_data function in hw/usb/dev-mtp.c due to an improper filename sanitization. When the guest device is mounted in read-write mode, this allows to read/write arbitrary files which may lead do DoS scenario OR possibly lead to code execution on the host.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2018-16867 resides within the QEMU virtualization platform's implementation of the Media Transfer Protocol (MTP) for USB devices. This flaw specifically affects versions of QEMU prior to 3.1.0 and represents a critical path traversal vulnerability that undermines the security boundaries between guest and host systems. The issue manifests in the usb_mtp_write_data function located within the hw/usb/dev-mtp.c source file, where inadequate input validation permits maliciously crafted MTP commands to manipulate file system access patterns. The vulnerability stems from insufficient sanitization of filenames passed through the MTP protocol, creating an exploitable condition that allows unauthorized file system operations beyond the intended scope of virtualized device access.
The technical exploitation of this vulnerability occurs when a guest operating system mounts a USB device configured with MTP in read-write mode, enabling the malicious guest to craft specific MTP commands that bypass normal file system access controls. The improper filename sanitization allows attackers to manipulate path traversal sequences such as ../ or ..\ that would normally be rejected by proper input validation mechanisms. This weakness creates a direct pathway for arbitrary file read and write operations on the host system, effectively breaking the isolation that virtualization environments are designed to maintain between guest and host environments. The vulnerability's impact is particularly severe because it can be leveraged to execute arbitrary code on the host system, potentially leading to complete compromise of the underlying physical infrastructure.
From an operational perspective, this vulnerability poses significant risks to virtualized environments where multiple users or untrusted guests may have access to USB devices through QEMU's MTP implementation. The potential for denial of service exists through file system corruption or resource exhaustion attacks, while the code execution capability could enable attackers to escalate privileges, install persistent backdoors, or exfiltrate sensitive data from the host system. The vulnerability's exploitation requires minimal privileges within the guest environment and can be particularly dangerous in cloud computing scenarios or shared hosting environments where guest isolation is paramount for security. Organizations running QEMU virtualization platforms without proper patching are exposed to risks that could affect their entire infrastructure, making this vulnerability a critical concern for system administrators and security professionals.
Mitigation strategies for CVE-2018-16867 primarily focus on immediate patching of QEMU installations to version 3.1.0 or later, which includes proper filename sanitization and path traversal prevention mechanisms. System administrators should also implement network segmentation and access controls to limit guest device access, disable unnecessary USB device functionalities, and monitor for suspicious file system activities. Additional protective measures include implementing virtualization-specific security controls such as SELinux or AppArmor policies to restrict host file system access from virtualized environments, employing network-based intrusion detection systems to monitor for suspicious MTP protocol usage, and conducting regular security audits of virtualization configurations. The vulnerability aligns with CWE-22 (Path Traversal) and represents a typical example of how protocol implementation flaws in virtualization software can create severe security implications, potentially mapping to ATT&CK technique T1059 (Command and Scripting Interpreter) and T1074 (Data Staged) for exploitation purposes. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive monitoring of their virtualization environments to detect potential exploitation attempts.