CVE-2018-12904 in Linux
Summary
by MITRE
In arch/x86/kvm/vmx.c in the Linux kernel before 4.17.2, when nested virtualization is used, local attackers could cause L1 KVM guests to VMEXIT, potentially allowing privilege escalations and denial of service attacks due to lack of checking of CPL.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-2018-12904 represents a critical flaw in the Linux kernel's virtual machine monitor implementation specifically affecting Intel VT-x virtualization technology. This issue exists within the vmx.c file in the x86 kernel architecture and impacts systems running Linux kernel versions prior to 4.17.2. The vulnerability is particularly concerning because it affects nested virtualization environments where guest virtual machines operate within other virtual machines, creating a complex attack surface that can be exploited by local malicious users.
The technical root cause of this vulnerability lies in insufficient validation of the Current Privilege Level (CPL) during nested virtualization operations. When L1 KVM guests utilize nested virtualization features, the kernel fails to properly verify the privilege level of operations being executed within the virtualized environment. This lack of CPL checking creates a condition where malicious code running within an L1 guest can manipulate virtual machine control structures in ways that trigger unintended VMEXIT events. The vulnerability specifically affects the VMX (Virtual Machine eXtensions) implementation that handles Intel's hardware virtualization features, making it a low-level architectural issue that impacts the fundamental security boundaries of the virtualization stack.
The operational impact of this vulnerability extends beyond simple privilege escalation capabilities to include potential denial of service conditions that can severely disrupt system operations. Local attackers with access to an L1 guest can exploit this flaw to force the virtual machine monitor to exit its execution context, effectively causing the guest to crash or become unresponsive. This behavior creates opportunities for both privilege escalation attacks where attackers can potentially elevate their privileges within the virtualized environment and denial of service scenarios that can impact the stability of the entire virtualization infrastructure. The vulnerability particularly affects systems that rely heavily on nested virtualization for containerization, cloud computing environments, or development testing scenarios where multiple layers of virtualization are common.
This vulnerability aligns with CWE-284, which addresses improper access control in software implementations, and demonstrates how insufficient privilege validation can create security weaknesses in virtualization environments. From an ATT&CK framework perspective, this represents a privilege escalation technique that leverages virtualization-specific weaknesses to gain elevated system access. The vulnerability also connects to ATT&CK technique T1055, which covers process injection and manipulation of system processes, as the exploitation can involve manipulating virtual machine control structures to achieve unauthorized access. Organizations using nested virtualization in production environments should immediately implement the kernel patch released in version 4.17.2 to mitigate this risk. Additionally, system administrators should consider implementing additional monitoring for unusual VMEXIT patterns and VM control structure modifications that could indicate exploitation attempts. The vulnerability highlights the importance of thorough security testing in complex virtualization environments where multiple abstraction layers can create unexpected security boundaries and attack vectors that require careful consideration during system design and deployment phases.