What’s Vulnerable › Vulnerabilities

CVE-2021-20267

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-28 · updated 2026-06-17
• Weakness: CWE-345

Description

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; from 17.0.0 before 17.1.3; 18.0.0 — fixed in 16.3.3, 17.1.3
• nova_libvirt container provided by the Red Hat OpenStack Platform: 10.0, 13.0, 16.1, 16.2

How to fix

Upgrade to a fixed version: OpenStack Neutron 16.3.3, 17.1.3. Check the vendor advisory for mitigations.

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1934330
• https://security.openstack.org/ossa/OSSA-2021-001.html
• https://bugzilla.redhat.com/show_bug.cgi?id=1934330
• https://security.openstack.org/ossa/OSSA-2021-001.html

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