CVE-2014-3968 in Xen
Summary
by MITRE
The HVMOP_inject_msi function in Xen 4.2.x, 4.3.x, and 4.4.x allows local guest HVM administrators to cause a denial of service (host crash) via a large number of crafted requests, which trigger an error messages to be logged.
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Analysis
by VulDB Data Team • 06/20/2021
The vulnerability identified as CVE-2014-3968 affects the Xen hypervisor version 4.2.x through 4.4.x, specifically within the HVMOP_inject_msi function. This flaw represents a critical security issue that enables local guest HVM administrators to execute a denial of service attack against the host system. The vulnerability stems from inadequate input validation and error handling within the hypervisor's message injection mechanism, which is designed to handle Microsoft's Message Signaled Interrupts for virtualized environments. When a malicious guest administrator submits a large volume of crafted MSI injection requests, the hypervisor's error handling routines become overwhelmed, leading to system instability and eventual host crash.
The technical implementation of this vulnerability involves the manipulation of the HVMOP_inject_msi hypercall interface, which is used to inject MSI interrupts into the virtualized environment. The flaw occurs because the hypervisor does not properly validate the size or frequency of MSI injection requests from guest administrators. This allows an attacker to flood the system with malformed or excessive requests, causing the hypervisor to log an excessive number of error messages and ultimately leading to a system crash. The vulnerability specifically targets the hypervisor's ability to manage interrupt handling within virtual machine environments, which is a fundamental aspect of virtualization security and stability.
From an operational impact perspective, this vulnerability presents a significant risk to cloud computing environments and virtualized infrastructures that rely on Xen hypervisors. Local guest administrators who gain access to virtual machines can exploit this flaw to cause complete host system crashes, potentially affecting multiple virtual machines running on the same physical host. The attack requires only local access to a guest VM, making it particularly dangerous in multi-tenant environments where guest administrators might have limited privileges but can still compromise the entire host infrastructure. This vulnerability directly impacts the availability and reliability of virtualized services, potentially causing widespread disruption in cloud environments.
The vulnerability maps to CWE-129 Input Validation and the ATT&CK technique T1499.004 for Network Denial of Service, as it enables an attacker to cause system-wide availability issues through targeted manipulation of hypervisor functions. Mitigation strategies include implementing strict rate limiting on MSI injection requests, enhancing input validation within the HVMOP_inject_msi function, and applying the official security patches released by the Xen project. System administrators should also consider implementing monitoring solutions to detect unusual patterns of MSI injection requests and isolate compromised virtual machines. The recommended remediation involves upgrading to Xen versions that have patched this vulnerability, as the original versions lack proper error handling mechanisms to prevent the accumulation of error messages that lead to system crashes. Organizations should also review their virtualization security policies to ensure that guest administrators have appropriate access controls and that proper isolation mechanisms are in place between different virtual environments.