CVE-2014-7188 in Xen
Summary
by MITRE
The hvm_msr_read_intercept function in arch/x86/hvm/hvm.c in Xen 4.1 through 4.4.x uses an improper MSR range for x2APIC emulation, which allows local HVM guests to cause a denial of service (host crash) or read data from the hypervisor or other guests via unspecified vectors.
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Analysis
by VulDB Data Team • 02/21/2022
The vulnerability identified as CVE-2014-7188 resides within the hypervisor component of Xen versions 4.1 through 4.4.x, specifically in the hvm_msr_read_intercept function located in arch/x86/hvm/hvm.c. This flaw represents a critical security issue that affects the x2APIC emulation functionality within the Hardware Virtual Machine (HVM) subsystem. The vulnerability stems from an improper Management Support Register (MSR) range validation mechanism that fails to correctly handle x2APIC register access patterns, creating a potential pathway for malicious exploitation.
The technical implementation flaw occurs when the hypervisor processes MSR read operations from HVM guests that are attempting to access x2APIC registers. The improper MSR range validation causes the hypervisor to either crash when encountering certain register access patterns or to inadvertently expose sensitive hypervisor memory contents to guest operating systems. This vulnerability operates at the intersection of virtualization security and processor architecture, leveraging the complex relationship between hardware virtualization and register access control mechanisms. The flaw specifically impacts the x2APIC (extended Advanced Programmable Interrupt Controller) emulation layer, which is responsible for handling advanced interrupt management features in modern processors.
From an operational perspective, this vulnerability presents a significant risk to virtualized environments as local HVM guests can exploit the flaw to either crash the host system or gain unauthorized access to hypervisor memory spaces. The potential impact extends beyond simple denial of service to include information disclosure, as the improper validation allows for data leakage from the hypervisor kernel to guest operating systems. This creates a scenario where a compromised guest can potentially access sensitive hypervisor data, including memory contents from other virtual machines running on the same host. The vulnerability's exploitation requires local access within an HVM guest, making it particularly concerning for multi-tenant cloud environments where guest isolation is paramount.
The mitigation strategies for CVE-2014-7188 involve upgrading to Xen versions 4.5 and later, which contain the necessary patches to properly validate MSR ranges during x2APIC emulation. Organizations should also implement monitoring for unusual host crashes or memory access patterns that might indicate exploitation attempts. Security teams should conduct comprehensive vulnerability assessments of their virtualization infrastructure and ensure that all Xen hosts are updated to patched versions. The vulnerability aligns with CWE-125 (Out-of-bounds Read) and CWE-200 (Information Exposure) categories, and represents a typical example of how hypervisor security flaws can lead to privilege escalation and information disclosure attacks. This vulnerability demonstrates the critical importance of proper input validation in hypervisor components and highlights the need for rigorous security testing of virtualization infrastructure. The ATT&CK framework categorizes this as a privilege escalation technique through hypervisor manipulation, emphasizing the need for comprehensive virtualization security measures and proper access controls in cloud and enterprise environments.