CVE-2022-37394 in Nova
Summary
by MITRE • 08/03/2022
An issue was discovered in OpenStack Nova before 23.2.2, 24.x before 24.1.2, and 25.x before 25.0.2. By creating a neutron port with the direct vnic_type, creating an instance bound to that port, and then changing the vnic_type of the bound port to macvtap, an authenticated user may cause the compute service to fail to restart, resulting in a possible denial of service. Only Nova deployments configured with SR-IOV are affected.
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Analysis
by VulDB Data Team • 08/30/2022
The vulnerability identified as CVE-2022-37394 represents a critical denial of service weakness within OpenStack Nova compute service that specifically impacts deployments utilizing SR-IOV (Single Root I/O Virtualization) configurations. This issue stems from a flawed handling of virtual network interface types during instance provisioning and port management processes, creating a scenario where authenticated users can manipulate the compute service restart mechanism through strategic port configuration changes. The vulnerability affects multiple release streams of Nova including versions prior to 23.2.2, 24.x versions before 24.1.2, and 25.x versions before 25.0.2, indicating a widespread impact across the OpenStack Nova ecosystem.
The technical flaw manifests when a user creates a neutron port with the direct vnic_type, subsequently binds an instance to that port, and then modifies the vnic_type of the bound port to macvtap. This sequence of operations triggers an inconsistency in Nova's internal state management and resource allocation logic, particularly when the compute service attempts to restart or reconfigure the affected virtual interfaces. The underlying issue lies in Nova's inability to properly handle the transition between different virtual interface types while maintaining consistent state information, leading to a cascade failure that prevents the compute service from restarting successfully. This behavior aligns with CWE-691, which addresses insufficient control flow management and represents a specific case of improper handling of dynamic configuration changes in virtualized environments.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire compute node availability within OpenStack deployments. When the compute service fails to restart, all instances hosted on that node become inaccessible, effectively rendering the node unusable for new instance creation or management operations. This creates a significant operational risk for cloud providers who rely on SR-IOV for high-performance networking requirements, as the vulnerability can be exploited by authenticated users with appropriate privileges to cause widespread service degradation. The attack vector requires minimal privileges but significant system access, making it particularly dangerous in multi-tenant environments where user isolation may be compromised. The vulnerability specifically targets SR-IOV configurations, which are commonly used in high-performance computing scenarios and network function virtualization deployments, amplifying the potential impact.
Mitigation strategies for this vulnerability should focus on immediate patch application to all affected Nova versions, with priority given to production environments utilizing SR-IOV configurations. Organizations should implement strict access controls and monitoring for port management operations, particularly those involving vnic_type changes, to detect and prevent unauthorized exploitation attempts. The recommended approach includes deploying the patched versions of Nova that contain fixes for the vnic_type handling logic and implementing network segmentation controls to limit user access to compute node resources. Additionally, administrators should consider implementing automated monitoring solutions that can detect compute service restart failures and alert security teams to potential exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 (Endpoint Denial of Service) and T1566.002 (Phishing via Service) as it represents a service-level denial of service that can be triggered through legitimate administrative operations. Organizations should also conduct thorough testing of patched environments to ensure that the fix does not introduce regressions in legitimate SR-IOV functionality while maintaining the security posture against this specific denial of service vector.