CVE-2014-9065 in Xen
Summary
by MITRE
common/spinlock.c in Xen 4.4.x and earlier does not properly handle read and write locks, which allows local x86 guest users to cause a denial of service (write denial or NMI watchdog timeout and host crash) via a large number of read requests, a different vulnerability to CVE-2014-9066.
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Analysis
by VulDB Data Team • 03/01/2022
The vulnerability identified as CVE-2014-9065 resides within the common/spinlock.c component of the Xen hypervisor version 4.4.x and earlier releases. This flaw represents a critical security issue that affects the hypervisor's handling of read and write locks in its spinlock implementation, which serves as a fundamental synchronization primitive for managing concurrent access to shared resources within the virtualized environment. The vulnerability specifically targets the x86 architecture guest users who can exploit this weakness to disrupt normal system operations.
The technical root cause of this vulnerability stems from improper handling of lock operations within the spinlock mechanism that governs how multiple virtual processors within the same domain interact with shared memory regions. When local x86 guest users initiate a large volume of read requests against the affected spinlock implementation, the hypervisor's lock management system becomes overwhelmed and unable to properly process these concurrent access attempts. This improper lock handling manifests in two primary failure modes that can lead to system instability and complete service disruption.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially cause complete system crashes through NMI (Non-Maskable Interrupt) watchdog timeouts. When the spinlock implementation fails to properly manage read requests, it can trigger cascading failures that result in the hypervisor's watchdog timer reaching its timeout threshold, leading to an automatic system reset or crash. This creates a scenario where a single malicious guest user can effectively compromise the entire host system's stability and availability, making it particularly dangerous in multi-tenant virtualized environments.
The vulnerability operates under the framework of CWE-362, which describes concurrent execution using shared resource vulnerabilities, and aligns with ATT&CK technique T1499.004 for Network Denial of Service. The attack vector specifically targets the hypervisor's lock management subsystem, which is a critical component of the virtualization layer that ensures proper resource allocation and prevents race conditions between virtual machines. This weakness allows attackers to exploit the fundamental synchronization mechanisms that protect shared resources, effectively creating a path to system instability.
Mitigation strategies for this vulnerability require immediate patching of the Xen hypervisor to versions that address the spinlock implementation flaws. System administrators should prioritize updating their hypervisor installations to versions that contain fixes for CVE-2014-9065, as the vulnerability directly impacts the stability of the entire virtualized infrastructure. Additionally, monitoring for unusual lock contention patterns and implementing proper resource isolation between guest domains can help detect and limit the impact of potential exploitation attempts. Organizations should also consider implementing additional security controls such as hypervisor hardening measures and regular vulnerability assessments to prevent similar issues from occurring in other components of their virtualization stack.