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CVE-2021-20267

24
FAUCET Score

CVE-2021-20267 describes a flaw in OpenStack Neutron's default Open vSwitch firewall rules, allowing server instances to impersonate IPv6 addresses of other systems. This vulnerability affects deployments utilizing the Open vSwitch driver in OpenStack Neutron versions prior to 15.3.3, 16.3.1, and 17.1.1, as well as Red Hat OpenStack Platform. With a CVSS score of 7.1 (HIGH), the vulnerability can be exploited remotely with low complexity, potentially leading to denial of service or traffic interception. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 16.3.3CPE matchmatch criteria
cpe:2.3:a:openstack:neutron:*:*:*:*:*:*:*:*
>= 17.0.0, < 17.1.3CPE matchmatch criteria
cpe:2.3:a:openstack:neutron:*:*:*:*:*:*:*:*
18.0.0CPE matchmatch criteria
cpe:2.3:a:openstack:neutron:18.0.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:a:redhat:openstack_platform:10.0:*:*:*:*:*:*:*
13.0CPE matchmatch criteria
cpe:2.3:a:redhat:openstack_platform:13.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.1HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
4.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.01%
Probability of exploitation in next 30 days
EPSS Percentile
59.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0101 is in the 56th percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

pippatch availablevia ghsa
Product: neutronFixed in: 16.3.1
pippatch availablevia ghsa
Product: neutronFixed in: 15.3.3
pippatch availablevia ghsa
Product: neutronFixed in: 17.1.1
redhatpatch availablevia nvd_reference
View patch
redhatvendor investigatingvia redhat_api
Product: Red Hat OpenStack Platform 16.1Fixed in: openstack-neutron
redhatno patchvia redhat_api
Product: Red Hat OpenStack Platform 16.2Fixed in: openstack-neutron

Vendor Advisories (2)

pipGHSA-w8hx-f868-pvchhigh

Openstack Neutron has Insufficient Verification of IPv6 addresses

May 24, 2022
redhatCVE-2021-20267Moderate

openstack-neutron: Anti-spoofing bypass using Open vSwitch

Nov 5, 2020

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
security.openstack.org / ossa/OSSA-2021-001.html
PatchVendor Advisory