CVE-2017-2583 in Linux
Summary
by MITRE
The load_segment_descriptor implementation in arch/x86/kvm/emulate.c in the Linux kernel before 4.9.5 improperly emulates a "MOV SS, NULL selector" instruction, which allows guest OS users to cause a denial of service (guest OS crash) or gain guest OS privileges via a crafted application.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2017-2583 resides within the Linux kernel's virtualization subsystem, specifically in the KVM (Kernel-based Virtual Machine) implementation. This flaw manifests in the load_segment_descriptor function located at arch/x86/kvm/emulate.c, where the kernel fails to properly handle the emulation of a MOV SS, NULL selector instruction. The issue affects Linux kernel versions prior to 4.9.5, creating a critical security gap that impacts virtualized environments. The vulnerability is particularly concerning because it operates at the hypervisor level, where it can be exploited by malicious guest operating systems to compromise the entire virtualization infrastructure.
The technical implementation flaw stems from inadequate validation and handling of null selector operations during segment descriptor loading in virtualized environments. When a guest OS attempts to execute a MOV SS, NULL selector instruction, the kernel's emulation logic fails to properly validate the operation, leading to potential memory corruption or privilege escalation. This occurs because the kernel does not adequately check the validity of the null selector before proceeding with the segment loading process, allowing malicious code to manipulate the processor state in ways that were not properly anticipated by the virtualization layer. The vulnerability represents a classic case of insufficient input validation and improper state management in hypervisor code.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can enable privilege escalation within virtualized environments. An attacker controlling a guest OS can leverage this flaw to either crash the guest operating system completely or potentially escalate privileges to gain access to the host system. This creates a significant risk for cloud environments, containerized deployments, and any infrastructure relying on KVM virtualization, where guest isolation is paramount for security. The vulnerability essentially undermines the fundamental security boundary between guest and host systems, potentially allowing attackers to break out of their isolated virtual environments.
Mitigation strategies for CVE-2017-2583 primarily involve upgrading to Linux kernel version 4.9.5 or later, which contains the necessary patches to properly handle null selector operations in the KVM emulation layer. System administrators should prioritize patching affected systems, particularly those running virtualized workloads where guest OS compromise could lead to broader infrastructure impact. Additionally, monitoring for suspicious activity related to virtual machine operations and implementing proper network segmentation can help limit the potential damage from exploitation attempts. This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and may be categorized under ATT&CK technique T1055 for privilege escalation through kernel exploits. Organizations should also consider implementing virtualization-specific security controls and regularly auditing their virtualized environments for similar implementation flaws that could be exploited for privilege escalation or denial of service attacks.