CVE-2021-20267

Name: CVE-2021-20267
Creator: NVD / NIST
Published: 2021-05-28T19:15:07.483+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.1/10EPSS 1.01%

Last modified Jun 17, 2026

CVE-2021-20267 is a high-severity vulnerability rated 7.1/10 on the CVSS scale. 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. EPSS estimates a 1.01% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.1/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H

EPSS Probability

1.01%

58.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-345

Affected Software

Vendor	Product	Versions
Openstack	Neutron	< 16.3.3
Openstack	Neutron	>= 17.0.0, < 17.1.3
Openstack	Neutron	18.0.0
Redhat	Openstack Platform	10.0
Redhat	Openstack Platform	13.0
Redhat	Openstack Platform	16.1
Redhat	Openstack Platform	16.2

References

https://bugzilla.redhat.com/show_bug.cgi?id=1934330Issue Tracking, Patch, Third Party Advisory
https://security.openstack.org/ossa/OSSA-2021-001.htmlPatch, Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1934330Issue Tracking, Patch, Third Party Advisory
https://security.openstack.org/ossa/OSSA-2021-001.htmlPatch, Vendor Advisory

Timeline

Published: May 28, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20267?

How severe is CVE-2021-20267?

CVE-2021-20267 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 1.01% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20267?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20267?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST