CVE-2018-10472 in Xen
Summary
by MITRE
An issue was discovered in Xen through 4.10.x allowing x86 HVM guest OS users (in certain configurations) to read arbitrary dom0 files via QMP live insertion of a CDROM, in conjunction with specifying the target file as the backing file of a snapshot.
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Analysis
by VulDB Data Team • 02/01/2020
This vulnerability exists within the Xen hypervisor version 4.10.x and earlier, specifically affecting x86 HVM guest operating systems under certain configurations. The flaw represents a critical privilege escalation and information disclosure issue that allows malicious guest users to access dom0 filesystem contents through a sophisticated attack vector involving QMP (QEMU Machine Protocol) commands and CDROM snapshot manipulation. The vulnerability stems from inadequate input validation and access control mechanisms within the hypervisor's handling of virtual CDROM devices and snapshot operations.
The technical implementation of this vulnerability involves a multi-step attack process where an unprivileged guest user can leverage QMP commands to perform live insertion of a CDROM device into the virtual machine. This particular configuration allows the attacker to specify arbitrary file paths as backing files for snapshots, effectively bypassing normal file system access controls. The flaw occurs because the hypervisor fails to properly validate the file paths specified in snapshot operations, permitting access to files outside the intended virtualized environment. This represents a direct violation of the hypervisor's isolation principles, where guest operating systems should be unable to access host system resources without explicit authorization.
The operational impact of this vulnerability is severe and far-reaching across virtualized environments. Dom0, which serves as the privileged management domain in Xen hypervisors, contains critical system files, configuration data, and potentially sensitive information that should remain isolated from guest operating systems. Successful exploitation enables attackers to read arbitrary files within dom0, potentially exposing system credentials, configuration files, network settings, and other sensitive data. This capability can lead to complete system compromise, as attackers can obtain information needed for further attacks, escalate privileges to full system control, or extract valuable data for lateral movement within the infrastructure. The vulnerability affects any environment where Xen hypervisors are used with x86 HVM guests and specific CDROM snapshot configurations are enabled.
Mitigation strategies for this vulnerability require immediate attention from system administrators and security teams. The primary recommendation is to upgrade to Xen version 4.11.0 or later, where the vulnerability has been addressed through improved input validation and access control mechanisms. Organizations should also implement network segmentation and disable unnecessary QMP interfaces where possible to limit attack surface. Additionally, monitoring for suspicious QMP commands and CDROM manipulation activities can help detect potential exploitation attempts. The vulnerability aligns with CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-284 (Improper Access Control) categories, and represents a technique that could be categorized under ATT&CK matrix tactic TA0005 (Defense Evasion) and TA0004 (Privilege Escalation) through the exploitation of hypervisor isolation boundaries. Regular security assessments of virtualization environments and implementation of principle of least privilege for QMP access should be enforced to prevent similar vulnerabilities from arising in the future.