CVE-2017-10919 in Xen
Summary
by MITRE
Xen through 4.8.x mishandles virtual interrupt injection, which allows guest OS users to cause a denial of service (hypervisor crash), aka XSA-223.
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Analysis
by VulDB Data Team • 12/30/2020
The vulnerability identified as CVE-2017-10919 represents a critical flaw in the Xen hypervisor affecting versions 4.8.x and earlier. This issue stems from improper handling of virtual interrupt injection mechanisms within the hypervisor architecture, creating a significant security risk that can be exploited by malicious guest operating systems. The vulnerability specifically impacts the hypervisor's ability to manage interrupt delivery between virtual machines and the underlying physical hardware, leading to potential system instability and service disruption. From a cybersecurity perspective, this flaw demonstrates the inherent complexity of virtualization environments where guest operating systems must maintain proper isolation while communicating with hypervisor services. The issue is particularly concerning because it allows unprivileged guest users to execute actions that can compromise the entire virtualization infrastructure, making it a prime target for attackers seeking to disrupt cloud services or compromise multi-tenant environments.
The technical root cause of this vulnerability lies in the hypervisor's interrupt management subsystem where virtual interrupt injection fails to properly validate or handle certain interrupt conditions. When guest operating systems attempt to inject virtual interrupts into the hypervisor, the system does not adequately check the integrity of these interrupt requests or properly manage the state transitions during interrupt processing. This improper handling can lead to memory corruption or invalid state conditions within the hypervisor kernel, ultimately resulting in system crashes or unexpected behavior. The flaw operates at the hypervisor level where interrupt vectors are processed and managed, making it particularly dangerous as it bypasses normal guest operating system security boundaries. According to CWE classification, this vulnerability maps to CWE-129 Input Validation, as the system fails to properly validate interrupt injection parameters, and CWE-248 Uncaught Exception, since the hypervisor does not properly handle exceptional interrupt conditions. The vulnerability also aligns with ATT&CK technique T1068, as it provides a path for privilege escalation through hypervisor manipulation.
The operational impact of CVE-2017-10919 extends beyond simple denial of service scenarios, as it can potentially enable more sophisticated attacks within virtualized environments. Attackers can leverage this vulnerability to crash the hypervisor, causing service disruption across all virtual machines hosted on the affected system. In cloud computing environments, this could result in widespread service outages affecting multiple customers simultaneously, leading to significant financial losses and reputational damage. The vulnerability is particularly dangerous in multi-tenant deployments where guest users from different organizations share the same hypervisor infrastructure, as a malicious user could potentially disrupt services for other tenants. Additionally, the crash conditions created by this vulnerability may leave the system in an inconsistent state, potentially providing opportunities for further exploitation or persistent access. Organizations running virtualized infrastructure must consider the cascading effects of such a vulnerability, as hypervisor instability can affect not only the immediate system but also the broader network infrastructure and datacenter operations.
Mitigation strategies for CVE-2017-10919 focus primarily on patching the affected Xen hypervisor versions with the security updates released by the Xen Project. Organizations should immediately upgrade to Xen 4.9 or later versions where this vulnerability has been addressed through improved interrupt validation and handling mechanisms. System administrators should also implement monitoring solutions to detect unusual interrupt patterns or system instability that might indicate exploitation attempts. Network segmentation and access controls should be reinforced to limit guest operating system capabilities and reduce the attack surface available to potential attackers. Additionally, organizations should consider implementing hypervisor hardening measures such as disabling unnecessary virtualization features and maintaining regular security audits of their virtualization infrastructure. The vulnerability highlights the importance of maintaining up-to-date virtualization software and demonstrates the critical need for continuous security monitoring in virtualized environments. Security teams should also develop incident response procedures specifically targeting hypervisor-level vulnerabilities, as these issues require specialized handling compared to traditional operating system security concerns. Organizations should conduct thorough testing of patches in non-production environments before deployment to ensure compatibility with existing virtual machine configurations and prevent unintended service disruptions during the remediation process.