CVE-2016-2140 in Compute
Summary
by MITRE
The libvirt driver in OpenStack Compute (Nova) before 2015.1.4 (kilo) and 12.0.x before 12.0.3 (liberty), when using raw storage and use_cow_images is set to false, allows remote authenticated users to read arbitrary files via a crafted qcow2 header in an ephemeral or root disk.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability CVE-2016-2140 represents a critical security flaw in the OpenStack Compute service known as Nova, specifically within its libvirt driver component. This vulnerability affects versions prior to 2015.1.4 (kilo release) and 12.0.3 (liberty release), creating a significant risk for cloud environments that utilize raw storage configurations. The flaw manifests when the use_cow_images parameter is explicitly set to false, which is a common configuration in certain OpenStack deployments. The vulnerability stems from inadequate input validation mechanisms within the qcow2 disk image handling process, allowing malicious actors to exploit the system through crafted malicious qcow2 headers.
The technical exploitation of this vulnerability occurs through a sophisticated attack vector that leverages the interaction between OpenStack Nova's libvirt driver and qcow2 disk image format processing. When a user with authentication credentials submits a malicious qcow2 header within an ephemeral or root disk image, the system fails to properly validate the header structure before processing it. This validation failure enables an attacker to manipulate the disk image parsing logic to traverse the filesystem and access arbitrary files on the host system. The vulnerability is particularly dangerous because it operates at the hypervisor level where the attacker can potentially access sensitive system files, configuration data, and other confidential information stored on the compute node.
The operational impact of this vulnerability extends far beyond simple unauthorized file access, as it fundamentally compromises the security isolation that virtual machines should maintain within a cloud environment. Attackers can potentially extract sensitive data including cloud credentials, configuration files, and other system information that could be used for further exploitation or lateral movement within the cloud infrastructure. The vulnerability affects the core security model of OpenStack deployments, as it allows authenticated users to bypass normal file system access controls and potentially escalate their privileges within the compute environment. This risk is particularly severe in multi-tenant cloud deployments where proper isolation between different users and projects is essential for maintaining security boundaries.
Organizations can mitigate this vulnerability through several strategic approaches that align with established security frameworks including the CWE classification for improper input validation and the MITRE ATT&CK framework's techniques for privilege escalation and credential access. The primary mitigation involves updating OpenStack Nova to versions 2015.1.4 or later for the kilo release, or 12.0.3 or later for the liberty release, which contain the necessary patches to address the qcow2 header validation issues. Additionally, administrators should consider implementing configuration hardening measures such as setting use_cow_images to true when raw storage is not strictly required, as this significantly reduces the attack surface. Network segmentation and access controls should be implemented to limit authentication access to only authorized personnel, while monitoring systems should be configured to detect anomalous disk image handling activities. The vulnerability also highlights the importance of proper input validation and secure coding practices, aligning with CWE-20 standards for improper input validation and emphasizing the need for robust sanitization of external inputs in hypervisor interfaces.