CVE-2014-2986 in Xen
Summary
by MITRE
The vgic_distr_mmio_write function in the virtual guest interrupt controller (GIC) distributor (arch/arm/vgic.c) in Xen 4.4.x, when running on an ARM system, allows local guest users to cause a denial of service (NULL pointer dereference and host crash) via unspecified vectors.
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Analysis
by VulDB Data Team • 05/12/2026
The vulnerability described in CVE-2014-2986 resides within the virtual guest interrupt controller implementation of the Xen hypervisor version 4.4.x, specifically affecting ARM-based systems. This issue manifests in the vgic_distr_mmio_write function which handles memory-mapped I/O write operations to the GIC distributor component. The GIC (Generic Interrupt Controller) serves as a critical interrupt management system in ARM architectures, responsible for handling interrupt routing between virtual machines and physical hardware. When operating within the Xen virtualization environment, the hypervisor must accurately manage interrupt delivery to prevent conflicts between guest operating systems and the host system.
The technical flaw stems from insufficient input validation and error handling within the vgic_distr_mmio_write function. When local guest users execute unspecified write operations to GIC distributor memory-mapped registers, the function fails to properly validate the target addresses or handle edge cases in the interrupt controller state. This leads to a NULL pointer dereference condition where the function attempts to access memory locations that have not been properly initialized or allocated. The vulnerability represents a classic case of improper error handling and memory management, which falls under CWE-476 which specifically addresses NULL pointer dereference issues in software implementations.
The operational impact of this vulnerability is severe and directly affects system stability and availability. Local guest users who exploit this vulnerability can trigger a host crash that results in complete denial of service for the entire virtualization environment. This means that the hypervisor itself becomes unstable and may require manual restart or complete system reboot to recover functionality. The crash occurs at the host level rather than remaining contained within the guest, making this particularly dangerous in production environments where multiple virtual machines share the same physical host. This vulnerability essentially allows a compromised guest to escalate its privileges and potentially disrupt services for all other virtual machines running on the same hypervisor instance.
The attack vector for this vulnerability is particularly concerning as it requires only local access within a guest operating system, making it accessible to malicious users who have already gained some level of system access. This aligns with ATT&CK technique T1059 which covers execution of malicious code within a compromised system, and T1499 which addresses denial of service attacks. The vulnerability's exploitation does not require special privileges or network access, making it an attractive target for attackers who have already established a foothold within the guest environment. Organizations using Xen 4.4.x on ARM systems should consider this vulnerability as a critical threat to their virtualization infrastructure security.
Mitigation strategies for CVE-2014-2986 should focus on immediate patching of the Xen hypervisor to version 4.5.0 or later, which contains the necessary fixes for the GIC distributor memory management issues. Additionally, administrators should implement strict monitoring of guest system behavior and consider isolation measures such as limiting guest privileges and implementing virtual machine resource controls. Network segmentation and access controls should be enhanced to prevent unauthorized local access to guest systems. The vulnerability also highlights the importance of comprehensive input validation and error handling in hypervisor code, emphasizing the need for regular security audits and code reviews of critical virtualization components. Organizations should also consider implementing intrusion detection systems to monitor for unusual patterns of memory-mapped I/O operations that might indicate exploitation attempts.