CVE-2014-5149 in Xen
Summary
by MITRE
Certain MMU virtualization operations in Xen 4.2.x through 4.4.x, when using shadow pagetables, are not preemptible, which allows local HVM guest to cause a denial of service (vcpu consumption) by invoking these operations, which process every page assigned to a guest, a different vulnerability than CVE-2014-5146.
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Analysis
by VulDB Data Team • 02/10/2022
The vulnerability identified as CVE-2014-5149 represents a critical flaw in the Xen hypervisor's memory management unit virtualization implementation that affects versions 4.2.x through 4.4.x. This issue specifically impacts systems utilizing shadow pagetables for memory virtualization, creating a scenario where local HVM (Hardware Virtual Machine) guests can exploit a fundamental design weakness in the hypervisor's memory management subsystem. The vulnerability stems from the non-preemptible nature of certain MMU virtualization operations, which means these operations cannot be interrupted or preempted during execution, leading to potential system resource exhaustion.
The technical flaw manifests in the hypervisor's handling of shadow pagetable operations that must process every page assigned to a guest virtual machine. When a malicious HVM guest invokes these specific memory management operations, the hypervisor enters a state where it cannot be interrupted, causing the virtual cpu to consume excessive system resources. This creates a denial of service condition where the affected vcpu becomes unresponsive and consumes disproportionate computational resources, effectively starving other virtual machines or system processes of necessary processing time. The vulnerability operates at the core of virtualization technology, specifically targeting the memory management unit's ability to handle page table operations efficiently and safely.
The operational impact of CVE-2014-5149 extends beyond simple resource exhaustion, as it represents a fundamental security weakness that can be exploited by local attackers within a virtualized environment. An attacker with access to an HVM guest can systematically consume all available vcpu resources by repeatedly invoking the vulnerable MMU operations, effectively rendering the system unusable for legitimate virtual machine operations. This vulnerability is particularly concerning because it operates at the hypervisor level, meaning that a compromised guest can affect the entire virtualization infrastructure. The flaw creates a persistent resource drain that can be difficult to detect and mitigate, as it appears to be a normal system behavior rather than an obvious attack vector, making it a significant concern for cloud providers and virtualization environments that host multiple tenants.
The vulnerability demonstrates a clear pattern that aligns with CWE-400, which describes unchecked resource consumption, and can be categorized under ATT&CK technique T1499.001, which involves resource exhaustion attacks. Organizations utilizing Xen hypervisors in production environments face significant risk from this vulnerability, as it allows for a straightforward denial of service attack that can be executed by any local user within a guest virtual machine. The attack vector is particularly dangerous because it does not require elevated privileges or complex exploitation techniques, making it accessible to a broad range of potential attackers. System administrators should implement immediate mitigations including upgrading to patched versions of Xen, implementing resource quotas for virtual machines, and monitoring for unusual vcpu consumption patterns that could indicate exploitation attempts. The vulnerability also underscores the importance of thorough testing of hypervisor security features and the need for preemptible operations in critical system components to prevent such resource exhaustion attacks from compromising overall system stability and availability.