CVE-2014-5147 in Xen
Summary
by MITRE
Xen 4.4.x, when running a 64-bit kernel on an ARM system, does not properly handle traps from the guest domain that use a different address width, which allows local guest users to cause a denial of service (host crash) via a crafted 32-bit process.
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Analysis
by VulDB Data Team • 06/05/2017
The vulnerability identified as CVE-2014-5147 represents a critical design flaw in the Xen hypervisor version 4.4.x when operating in ARM 64-bit kernel environments. This issue stems from the hypervisor's improper handling of trap mechanisms that occur when guest domains utilize different address widths, creating a fundamental mismatch in memory management and privilege level transitions. The vulnerability specifically affects systems where a 64-bit hypervisor kernel executes on ARM architecture while guest domains may attempt to use 32-bit processes, leading to inconsistent trap handling between the two address modes.
The technical root cause of this vulnerability lies in the hypervisor's trap handling mechanism that fails to properly validate and process trap requests originating from guest domains when they operate under different address width configurations. When a 32-bit process within a guest domain triggers a trap condition, the hypervisor's kernel code does not correctly account for the address width difference between the guest's 32-bit execution context and the host's 64-bit kernel environment. This mismatch results in improper memory access patterns and invalid privilege transitions that ultimately lead to system instability and host kernel crashes. The flaw manifests as a failure in the hypervisor's virtualization layer to properly translate and handle trap vectors that cross the address width boundary, creating a condition where malicious or malformed 32-bit processes can force the host system into an unrecoverable state.
From an operational perspective, this vulnerability presents a significant risk to virtualized environments running Xen hypervisors on ARM 64-bit systems, particularly in cloud computing and infrastructure virtualization deployments where multiple guest domains operate concurrently. The local privilege escalation aspect means that any user within a guest domain can potentially trigger a host crash, effectively creating a denial of service condition that impacts the entire virtualization platform. This vulnerability is particularly concerning in multi-tenant environments where guest isolation is critical, as it allows one guest domain to potentially disrupt services for other guests and the underlying host system. The impact extends beyond simple service disruption to include potential data loss and system downtime that can affect business continuity and service availability.
The security implications of this vulnerability align with CWE-122, which addresses improper restriction of operations within a recognized security boundary, and can be mapped to ATT&CK technique T1499.004, which covers "Evasion: Virtualization/Sandbox Evasion" through system instability. Organizations should implement immediate mitigations including updating to Xen hypervisor versions that address this specific trap handling issue, implementing strict guest domain isolation policies, and monitoring for anomalous trap behavior that might indicate exploitation attempts. Additionally, system administrators should consider disabling 32-bit guest support where possible and ensure that all virtualization environments undergo regular security assessments to identify similar architectural weaknesses. The vulnerability demonstrates the complexity of virtualization security and the critical importance of proper privilege boundary enforcement in hypervisor implementations, particularly when dealing with mixed architecture environments where different address widths create additional attack surfaces.