CVE-2018-19406 in Linux
Summary
by MITRE
kvm_pv_send_ipi in arch/x86/kvm/lapic.c in the Linux kernel through 4.19.2 allows local users to cause a denial of service (NULL pointer dereference and BUG) via crafted system calls that reach a situation where the apic map is uninitialized.
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Analysis
by VulDB Data Team • 06/11/2023
The vulnerability identified as CVE-2018-19406 resides within the Linux kernel's KVM (Kernel-based Virtual Machine) implementation, specifically in the kvm_pv_send_ipi function located in arch/x86/kvm/lapic.c. This flaw represents a critical NULL pointer dereference issue that can be exploited by local attackers to trigger a kernel BUG, effectively causing a denial of service condition. The vulnerability manifests when crafted system calls are executed that lead to an uninitialized apic map scenario, which the kernel fails to properly handle during virtual machine interrupt processing operations.
The technical root cause of this vulnerability stems from inadequate input validation and state management within the KVM subsystem's local APIC (Advanced Programmable Interrupt Controller) handling code. When virtual machines are configured with paravirtualized interrupt delivery mechanisms, the kernel must properly initialize and maintain the APIC map structure that facilitates interrupt routing between virtual processors. However, under specific conditions involving crafted system calls, the apic map remains uninitialized while the kvm_pv_send_ipi function attempts to dereference it, resulting in a kernel panic and system crash. This represents a classic case of improper state handling that violates fundamental kernel security principles and can be classified under CWE-476 as NULL pointer dereference.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged to crash the entire kernel or virtual machine host system, potentially affecting multiple virtual machines running on the same physical hardware. Local users with limited privileges can exploit this weakness without requiring elevated permissions, making it particularly dangerous in multi-tenant environments or systems where untrusted users have access to kernel interfaces. The vulnerability affects all Linux kernel versions through 4.19.2, representing a substantial attack surface given the widespread adoption of these kernel versions across enterprise and cloud environments.
Mitigation strategies for CVE-2018-19406 should prioritize immediate kernel updates to versions that contain the appropriate patches addressing the uninitialized apic map handling issue. System administrators should also implement monitoring solutions to detect anomalous system call patterns that might indicate exploitation attempts, particularly focusing on virtualization-related interfaces and interrupt management functions. Additional defensive measures include restricting local user access to kernel interfaces where possible, implementing proper kernel lockdown mechanisms, and conducting thorough security audits of virtualization configurations. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service, potentially enabling adversaries to establish persistent access or disrupt critical services within virtualized environments. The patch for this vulnerability specifically addresses the missing initialization check in the APIC map structure, ensuring that proper validation occurs before any pointer dereference operations are executed, thereby preventing the kernel from crashing due to invalid memory access patterns.