CVE-2018-14636 in openstack-neutron
Summary
by MITRE
Live-migrated instances are briefly able to inspect traffic for other instances on the same hypervisor. This brief window could be extended indefinitely if the instance's port is set administratively down prior to live-migration and kept down after the migration is complete. This is possible due to the Open vSwitch integration bridge being connected to the instance during migration. When connected to the integration bridge, all traffic for instances using the same Open vSwitch instance would potentially be visible to the migrated guest, as the required Open vSwitch VLAN filters are only applied post-migration. Versions of openstack-neutron before 13.0.0.0b2, 12.0.3, 11.0.5 are vulnerable.
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Analysis
by VulDB Data Team • 05/08/2023
This vulnerability represents a critical network isolation failure within OpenStack neutron deployments that leverages the specific behavior of Open vSwitch integration bridges during live migration operations. The flaw occurs when virtual machines are migrated between hypervisors without proper network segmentation controls, creating a temporary window where migrated instances can potentially access network traffic from other instances sharing the same hypervisor. This represents a direct violation of network isolation principles that are fundamental to cloud security architectures and can be classified under CWE-284 Access Control Issues. The vulnerability specifically exploits the timing gap between when an instance connects to the Open vSwitch integration bridge during migration and when the proper VLAN filtering rules are applied post-migration, creating a window where traffic inspection becomes possible across multiple instances.
The technical implementation of this vulnerability stems from the asynchronous nature of network configuration updates during live migration processes. During migration, the instance's network interface connects to the integration bridge before the necessary security policies and VLAN filters are properly configured, allowing the migrated instance to potentially observe network traffic from other instances that share the same Open vSwitch infrastructure. This timing gap creates a window where network traffic from other VMs on the same hypervisor becomes visible to the migrated guest, essentially allowing for network sniffing and potential data exfiltration. The vulnerability is particularly concerning because it can be extended indefinitely if administrators set the instance's port administratively down before migration and keep it down after migration, effectively maintaining the exposure window for extended periods. This behavior aligns with ATT&CK technique T1046 Network Service Scanning and T1071 Application Layer Protocol Network Protocol Command and Control, as it enables unauthorized network reconnaissance and potential lateral movement within the same hypervisor environment.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks including man-in-the-middle scenarios, credential theft, and network reconnaissance across multiple tenant instances. Attackers could leverage this vulnerability to gain insights into network topology, identify services running on other instances, and potentially extract sensitive data transmitted over the network. The risk is particularly elevated in multi-tenant environments where isolation between different customers or projects is paramount, as this vulnerability could allow one tenant's instance to observe another tenant's network traffic. This represents a significant compromise of the principle of least privilege and can be classified as a privilege escalation vulnerability within the network security context, as it allows for unauthorized access to network resources that should be isolated. Organizations using OpenStack deployments with versions prior to 13.0.0.0b2, 12.0.3, or 11.0.5 are particularly at risk, as these versions lack the necessary fixes to address the timing gap in network policy application during live migration operations.
Mitigation strategies for this vulnerability should focus on implementing immediate network policy enforcement during migration operations and ensuring proper VLAN filtering is applied before instances connect to integration bridges. Organizations should upgrade to patched versions of openstack-neutron that address this specific timing issue in network policy application. Additionally, implementing strict network segmentation policies, monitoring for unusual network behavior during migration events, and ensuring that administrative port down operations are properly tracked and managed can help reduce the exposure window. The fix typically involves modifying the migration process to ensure that VLAN filters are applied immediately upon connection to the integration bridge rather than waiting for post-migration configuration. Organizations should also consider implementing network monitoring solutions that can detect and alert on potential network isolation violations during live migration operations, as this vulnerability can be exploited without direct user interaction and may go unnoticed for extended periods. This vulnerability underscores the importance of proper network security design in virtualized environments and the critical need for synchronization between compute and network configuration updates during dynamic operations like live migration.