CVE-2021-20267: Openstack Neutron

High severity, CVSS 7.1. EPSS: 1% chance of exploitation in the next 30 days.

A flaw was found in openstack-neutron's default Open vSwitch firewall rules. By sending carefully crafted packets, anyone in control of a server instance connected to the virtual switch can impersonate the IPv6 addresses of other systems on the network, resulting in denial of service or in some cases possibly interception of traffic intended for other destinations. Only deployments using the Open vSwitch driver are affected. Source: OpenStack project. Versions before openstack-neutron 15.3.3, openstack-neutron 16.3.1 and openstack-neutron 17.1.1 are affected.

Affected products

• Openstack Neutron: before 16.3.3 (fixed in 16.3.3); from 17.0.0, before 17.1.3 (fixed in 17.1.3); version 18.0.0 only
• Red Hat Openstack Platform: version 10.0 only; version 13.0 only; version 16.1 only; version 16.2 only

Published 2021-05-28. Last modified 2026-06-17.