CVE-2013-1919 in Xen
Summary
by MITRE
Xen 4.2.x and 4.1.x does not properly restrict access to IRQs, which allows local stub domain clients to gain access to IRQs and cause a denial of service via vectors related to "passed-through IRQs or PCI devices."
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Analysis
by VulDB Data Team • 05/10/2021
The vulnerability identified as CVE-2013-1919 affects Xen hypervisor versions 4.2.x and 4.1.x, representing a critical access control flaw that undermines the fundamental security model of virtualization environments. This issue stems from insufficient restrictions on interrupt request (IRQ) handling within the hypervisor's stub domain implementation, creating a pathway for malicious local users to exploit the system's interrupt management mechanisms. The vulnerability specifically targets the improper handling of passed-through IRQs and PCI devices, which are essential components for hardware virtualization and device passthrough functionality.
The technical flaw manifests in the hypervisor's failure to properly validate and enforce access controls for IRQ resources that are intended to be isolated between virtual machines and the host system. When stub domain clients attempt to access IRQs that have been passed through to guest domains, the system does not adequately verify the requesting entity's privileges or the legitimacy of the access request. This weakness allows local users within the stub domain to manipulate interrupt handling mechanisms and potentially gain unauthorized access to IRQ resources that should remain restricted. The vulnerability's impact is particularly concerning because IRQs serve as critical system interrupt vectors that can be leveraged for both privilege escalation and denial of service attacks.
The operational impact of this vulnerability extends beyond simple access control violations, as it can be exploited to cause significant system instability and denial of service conditions. Attackers can leverage the improper IRQ access controls to disrupt normal system operations by manipulating interrupt handlers or causing conflicts in interrupt routing. When passed-through IRQs or PCI devices are involved, the attack surface expands to include hardware-level resources that are typically protected from unauthorized access. This can result in complete system crashes, guest VM disruptions, or the compromise of the entire virtualization environment's integrity. The vulnerability essentially undermines the hypervisor's ability to maintain proper isolation between domains, potentially allowing malicious actors to escalate privileges or cause cascading failures across multiple virtual machines.
Mitigation strategies for CVE-2013-1919 should focus on implementing proper access control enforcement and privilege validation for IRQ resources within the Xen hypervisor. Organizations should immediately upgrade to Xen versions that address this vulnerability, specifically those beyond the affected 4.1.x and 4.2.x releases where proper IRQ access controls have been implemented. System administrators should also consider implementing additional monitoring and logging of IRQ access patterns to detect potential exploitation attempts. The vulnerability aligns with CWE-284, which addresses improper access control, and can be mapped to ATT&CK techniques involving privilege escalation and denial of service. Security teams should conduct thorough vulnerability assessments to identify any systems running affected Xen versions and ensure proper patch management procedures are in place to prevent exploitation.