CVE-2021-20267

mediumpriority · track · 28OT risk · elevatedEPSS 0.010 · 63 %ileEURUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
1.02% (63rd) EPSS
CVSS 5.5 · medium
Is it mine?
17 products
Check your exposure
Who says so?
5 sources
cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

7.1
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5.5–7.1

v2.05.5mediumAV:N/AC:L/Au:S/C:P/I:N/A:Pprimary · NVD / NIST USexploitability 8 · impact 4.9
v3.17.1highCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Hprimary · NVD / NIST USexploitability 2.8 · impact 4.2
v3.17.1highAV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Hsecondary · FSTEC (BDU) RU
v3.17.1highCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Hsecondary · OSV
v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)
02

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-345USCWE-345USCWE-345US
03

affected products (17)

Products and version ranges known to be affected.

04

advisories (2)

Vendor and ecosystem advisories describing this.

  • GHSA-w8hx-f868-pvchOpenstack Neutron has Insufficient Verification of IPv6 addresses2022-05-24ghsa · osvUS

    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.

  • PYSEC-2021-1362021-05-28vendor · osvUS

    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.

05

also known as (7)

Other names and identifiers for this entity.

06

sources

Which sources assert this record, and when.

cnnvdenisa_euvdfstec_bduosvnvdNVDCVE.orgMITRE
published 2021-05-28modified 2026-06-17
07

references (8)

External citations — patches, advisories, analysis.

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