CVE-2015-1563 in Xen
Summary
by MITRE
The ARM GIC distributor virtualization in Xen 4.4.x and 4.5.x allows local guests to cause a denial of service by causing a large number messages to be logged.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability identified as CVE-2015-1563 resides within the ARM Generic Interrupt Controller (GIC) distributor virtualization implementation in the Xen hypervisor versions 4.4.x and 4.5.x. This issue manifests as a local privilege escalation vulnerability that enables guest operating systems running within Xen virtual machines to exploit the hypervisor's interrupt handling mechanisms. The flaw specifically targets the virtualization layer responsible for managing interrupt distribution between physical hardware and virtual machines, creating a pathway for malicious guest code to manipulate the interrupt controller's behavior. The vulnerability operates through the hypervisor's logging mechanisms, where excessive interrupt messages trigger resource exhaustion and system instability.
The technical exploitation of this vulnerability occurs when a local guest operating system generates an excessive volume of interrupt messages that are processed by the GIC distributor virtualization component. This behavior causes the hypervisor to log an overwhelming number of entries, leading to system resource exhaustion and ultimately resulting in a denial of service condition. The flaw stems from inadequate input validation and resource management within the interrupt logging subsystem, where the hypervisor fails to properly throttle or limit the rate of interrupt message processing. The vulnerability is particularly concerning because it operates at the hypervisor level, allowing guest users to affect the stability of the entire virtualization environment rather than just their individual virtual machine.
From an operational impact perspective, this vulnerability poses significant risks to virtualized environments that rely on Xen hypervisors for hosting multiple guest operating systems. The denial of service condition can affect not only the compromised virtual machine but potentially impact other virtual machines sharing the same physical host, leading to cascading failures and service disruption. The vulnerability's exploitation requires only local access within a guest environment, making it particularly dangerous in multi-tenant cloud deployments where isolation between guests is expected. Organizations using Xen versions 4.4.x and 4.5.x face potential system instability, performance degradation, and complete service outages when this vulnerability is exploited.
The vulnerability aligns with CWE-400, which addresses unchecked resource consumption, and specifically relates to improper handling of interrupt message processing in virtualized environments. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1068, which involves local privilege escalation through system vulnerabilities. The attack vector involves a guest user leveraging the hypervisor's own logging mechanisms against itself, creating a self-inflicted denial of service that undermines the fundamental security model of virtualization. Mitigation strategies should include immediate patching of Xen hypervisor versions to address the interrupt handling logic and implementation of proper rate limiting and resource allocation controls within the virtualization environment.
Organizations should implement comprehensive monitoring of interrupt logging activities and establish baseline thresholds for normal system behavior to detect potential exploitation attempts. The recommended remediation involves upgrading to Xen hypervisor versions that contain fixes for the GIC distributor virtualization implementation, specifically addressing the interrupt message handling and logging mechanisms. Additionally, implementing proper resource isolation and limiting the number of concurrent interrupt messages that can be processed by the hypervisor helps prevent exploitation. System administrators should also consider implementing intrusion detection systems that can monitor for unusual logging patterns and excessive interrupt message generation within virtualized environments. The vulnerability demonstrates the critical importance of proper resource management in hypervisor implementations and highlights the need for thorough security testing of virtualization components before deployment in production environments.