CVE-2009-3638 in Linux
Summary
by MITRE
Integer overflow in the kvm_dev_ioctl_get_supported_cpuid function in arch/x86/kvm/x86.c in the KVM subsystem in the Linux kernel before 2.6.31.4 allows local users to have an unspecified impact via a KVM_GET_SUPPORTED_CPUID request to the kvm_arch_dev_ioctl function.
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Analysis
by VulDB Data Team • 08/24/2021
The vulnerability identified as CVE-2009-3638 represents a critical integer overflow flaw within the Kernel-based Virtual Machine (KVM) subsystem of the Linux kernel. This vulnerability exists in the kvm_dev_ioctl_get_supported_cpuid function located in arch/x86/kvm/x86.c, specifically affecting Linux kernel versions prior to 2.6.31.4. The flaw manifests when processing KVM_GET_SUPPORTED_CPUID requests through the kvm_arch_dev_ioctl function, creating a potential vector for local privilege escalation or system instability. The integer overflow occurs during the handling of CPUID information retrieval, where improper bounds checking allows malicious input to cause arithmetic overflow conditions that can corrupt memory structures or alter program execution flow.
From a technical perspective, this vulnerability falls under CWE-190, which categorizes integer overflow conditions that can lead to buffer overflows or other memory corruption issues. The flaw specifically exploits the lack of proper input validation when processing CPUID request parameters, allowing an attacker to manipulate the size or count parameters in a way that exceeds the maximum value representable by the integer type used in the computation. The KVM subsystem, designed to provide hardware virtualization capabilities for linux systems, becomes vulnerable when local users can craft malicious ioctl requests that trigger this overflow condition. This represents a classic case of insufficient input sanitization where the kernel fails to validate that the requested CPUID information size remains within acceptable bounds before processing.
The operational impact of CVE-2009-3638 extends beyond simple system instability, potentially enabling local users to escalate privileges or cause denial of service conditions within virtualized environments. Since KVM is widely used for virtualization in enterprise and cloud computing environments, this vulnerability could be exploited in scenarios where unprivileged users have access to virtual machine interfaces or kernel device files. The unspecified nature of the impact indicates that depending on the specific overflow conditions and memory layout, attackers could potentially manipulate kernel memory structures, leading to privilege escalation or arbitrary code execution in kernel space. This vulnerability directly relates to ATT&CK technique T1068, which covers local privilege escalation through kernel exploits, making it particularly concerning for systems running virtualized workloads.
Mitigation strategies for this vulnerability require immediate kernel version updates to 2.6.31.4 or later, where the integer overflow has been addressed through proper input validation and bounds checking. System administrators should implement comprehensive patch management procedures to ensure all virtualized environments receive timely security updates. Additional protective measures include restricting access to KVM device files and ioctl interfaces, implementing proper user privilege controls, and monitoring for suspicious ioctl activity patterns. Organizations running KVM-based virtualization should also consider implementing kernel hardening techniques such as stack canaries, address space layout randomization, and kernel module signing to reduce the potential impact of similar vulnerabilities. The vulnerability demonstrates the critical importance of input validation in kernel subsystems and highlights why security reviews of virtualization components are essential for maintaining system integrity in modern computing environments.