CVE-2014-3645 in Linux
Summary
by MITRE
arch/x86/kvm/vmx.c in the KVM subsystem in the Linux kernel before 3.12 does not have an exit handler for the INVEPT instruction, which allows guest OS users to cause a denial of service (guest OS crash) via a crafted application.
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Analysis
by VulDB Data Team • 02/23/2022
The vulnerability identified as CVE-2014-3645 resides within the Kernel-based Virtual Machine (KVM) subsystem of the Linux kernel, specifically in the x86 virtualization implementation. This flaw affects kernel versions prior to 3.12 and represents a critical design oversight in the virtualization layer that governs Intel Virtualization Technology (VT) instructions. The vulnerability manifests when the KVM subsystem processes certain virtualization instructions without proper handling mechanisms, creating a potential attack surface for malicious guest operating systems.
The technical root cause of this vulnerability stems from the absence of an exit handler for the INVEPT (Invalidate Extended Page Table) instruction within the VMX (Virtual Machine Extensions) component of KVM. The INVEPT instruction is a privileged Intel VT instruction designed to invalidate specific entries in the extended page table structure, which is essential for maintaining memory consistency in virtualized environments. When a guest operating system attempts to execute this instruction, the kernel lacks the proper interception and handling mechanism, leading to an uncontrolled execution path that results in system instability.
This vulnerability operates under the broader category of improper handling of virtualization instructions, which falls under CWE-248, or "Exception Handling" in the Common Weakness Enumeration catalog. The flaw enables a guest operating system user to exploit the missing exit handler through a crafted application that executes the INVEPT instruction. The attack vector is particularly concerning because it requires minimal privileges within the guest environment and can be executed by any application running in the virtualized environment, making it a significant threat to virtualization security.
The operational impact of CVE-2014-3645 is severe, as it allows for a denial of service condition that can crash the entire guest operating system. This occurs because the missing exit handler causes the virtualization layer to fail when processing the INVEPT instruction, leading to a kernel panic or system crash. The vulnerability affects all Linux systems running kernel versions before 3.12 that utilize KVM for virtualization, potentially compromising the availability of virtualized workloads and services. This type of vulnerability directly aligns with ATT&CK technique T1499.001, which involves the use of system shutdown/reboot attacks to deny service to legitimate users.
The implications extend beyond simple system crashes, as this vulnerability can be leveraged by attackers to disrupt virtualized environments and potentially escalate their attacks. The lack of proper instruction handling creates a pathway for malicious actors to gain control over virtual machine operations, potentially leading to more sophisticated attacks such as privilege escalation or data compromise. Organizations relying on KVM-based virtualization for cloud computing, containerization, or server consolidation are particularly vulnerable to this flaw, as it undermines the fundamental security guarantees provided by virtualization technologies.
Mitigation strategies for this vulnerability include immediate kernel updates to version 3.12 or later, which contain the necessary exit handler implementation for the INVEPT instruction. System administrators should also consider implementing additional monitoring and logging of virtualization-related activities to detect potential exploitation attempts. The vulnerability highlights the importance of comprehensive virtualization instruction handling and proper kernel security auditing, particularly in systems where multiple virtual machines share the same physical hardware resources. Organizations should also review their virtualization security policies and ensure that guest operating systems are properly isolated and monitored to prevent exploitation of such fundamental virtualization flaws.