CVE-2018-19407 in Linux
Summary
by MITRE
The vcpu_scan_ioapic function in arch/x86/kvm/x86.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 ioapic is uninitialized.
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Analysis
by VulDB Data Team • 06/11/2023
The vulnerability identified as CVE-2018-19407 resides within the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem, specifically in the vcpu_scan_ioapic function located at arch/x86/kvm/x86.c. This flaw represents a critical NULL pointer dereference issue that can be exploited by local attackers to trigger a system crash and denial of service condition. The vulnerability affects Linux kernel versions through 4.19.2, making it a widespread concern across numerous system deployments that utilize virtualization capabilities.
The technical nature of this vulnerability stems from inadequate input validation and error handling within the KVM subsystem's IOAPIC (I/O Advanced Programmable Interrupt Controller) management code. When crafted system calls are executed, they can manipulate the kernel's virtual machine execution environment in such a way that the ioapic structure remains uninitialized while the vcpu_scan_ioapic function attempts to access it. This creates a scenario where a NULL pointer dereference occurs, leading to an immediate kernel panic and system crash. The vulnerability manifests as a BUG message in kernel logs, indicating the kernel's inability to handle the unexpected NULL reference gracefully.
The operational impact of this vulnerability extends beyond simple denial of service, as it can compromise the stability and reliability of virtualized environments. In production systems where KVM virtual machines are actively running, a local user with access to the system can exploit this vulnerability to crash the entire kernel, potentially affecting all running virtual machines and causing data loss or service interruption. The local nature of the exploit means that any user with minimal system access can trigger this condition, making it particularly dangerous in multi-tenant environments or systems where privilege separation is not strictly enforced.
This vulnerability aligns with CWE-476, which identifies NULL pointer dereference as a common weakness in software development, and demonstrates how virtualization-specific code can introduce unexpected failure points. The ATT&CK framework categorizes this as a privilege escalation technique through kernel exploitation, as local users can leverage this vulnerability to gain more significant control over system resources. The issue particularly affects systems running kernel versions 4.19.2 and earlier, making it essential for administrators to implement timely kernel updates and patches to prevent exploitation.
Mitigation strategies for CVE-2018-19407 primarily involve applying the official kernel patches released by the Linux kernel development team. System administrators should prioritize updating to kernel versions 4.19.3 or later, where the vulnerability has been addressed through proper initialization checks and error handling mechanisms. Additionally, implementing proper access controls and privilege separation can reduce the attack surface, as local users with minimal privileges should not be able to execute the specific system calls that trigger this condition. Monitoring for kernel BUG messages and system crashes can also help identify potential exploitation attempts, while maintaining up-to-date security patches ensures protection against similar vulnerabilities in the virtualization subsystem.