CVE-2012-0045 in Linux
Summary
by MITRE
The em_syscall function in arch/x86/kvm/emulate.c in the KVM implementation in the Linux kernel before 3.2.14 does not properly handle the 0f05 (aka syscall) opcode, which allows guest OS users to cause a denial of service (guest OS crash) via a crafted application, as demonstrated by an NASM file.
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Analysis
by VulDB Data Team • 09/26/2024
The vulnerability identified as CVE-2012-0045 resides within the Kernel-based Virtual Machine (KVM) implementation in the Linux kernel, specifically affecting versions prior to 3.2.14. This issue manifests in the em_syscall function located in arch/x86/kvm/emulate.c, which is responsible for handling system call emulation within virtualized environments. The flaw represents a critical oversight in the virtualization layer that could be exploited by malicious actors within guest operating systems to disrupt normal system operations. The vulnerability is particularly concerning because it affects the foundational virtualization capabilities that many cloud environments and virtualized deployments rely upon.
The technical flaw stems from improper handling of the 0f05 opcode, which corresponds to the x86 system call instruction. When a guest operating system executes this specific opcode, the KVM implementation fails to properly validate or process the system call emulation, leading to a potential kernel panic or system crash. This occurs because the em_syscall function does not adequately account for the specific conditions under which the syscall instruction might be executed within a virtualized context. The vulnerability is triggered when a crafted application within the guest OS attempts to execute the syscall instruction, causing the hypervisor to enter an undefined state that results in system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within virtualized environments. Attackers could leverage this flaw to cause persistent system crashes, potentially leading to data loss or service disruption in virtualized infrastructures. The demonstration using NASM files shows that the vulnerability can be reliably exploited through standard assembly language constructs, making it accessible to attackers with basic knowledge of x86 assembly. This vulnerability undermines the security model of virtualization by allowing guest users to directly impact the stability of the host system, creating a potential escalation path that violates the fundamental isolation principles of virtualized environments.
Mitigation strategies for CVE-2012-0045 primarily involve upgrading the Linux kernel to version 3.2.14 or later, where the em_syscall function has been properly patched to handle the 0f05 opcode correctly. System administrators should prioritize this update across all virtualized environments, particularly those hosting sensitive workloads or multiple tenants. Organizations should also implement monitoring solutions to detect unusual system crash patterns that might indicate exploitation attempts. From a cybersecurity perspective, this vulnerability aligns with CWE-248, representing an unchecked exception in a system call handler, and could be categorized under ATT&CK technique T1059.007 for execution through system services. The patch addresses the root cause by implementing proper validation mechanisms for system call emulation, ensuring that guest operating systems cannot trigger kernel-level crashes through malformed syscall instructions. Additionally, security teams should consider implementing virtualization-specific security controls and monitoring to prevent unauthorized exploitation of similar vulnerabilities in the hypervisor layer.