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Fencer Vulns
medium 6.5

CVE-2021-40085 json

OpenStack Neutron vulnerable to authenticated attackers reconfiguring dnsmasq via crafted extra_dhcp_opts value

published 2021-08-31 5 y ago modified 2026-06-17 4 mo ago also GHSA-fh73-gjvg-349c , PYSEC-2021-361 , EUVD-2021-0145

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.9%
EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

An issue was discovered in OpenStack Neutron before 16.4.1, 17.x before 17.2.1, and 18.x before 18.1.1. Authenticated attackers can reconfigure dnsmasq via a crafted extra_dhcp_opts value.

Patch / fix

  • pypi neutron 16.4.1, 17.2.1, 18.1.1
  • openstack neutron 16.4.1, 17.2.1, 18.1.1
  • neutron Debian 14, Debian 13, Debian 12 2:18.1.0-3

debian advisories DEBIAN-CVE-2021-40085

  • neutron Ubuntu 18.04 LTS 2:12.1.1-0ubuntu8.1
  • neutron Ubuntu 20.04 LTS 2:16.4.2-0ubuntu6.2

ubuntu advisories UBUNTU-CVE-2021-40085

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python3-neutron openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron-ml2 openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron-common openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron-rpc-server openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron-linuxbridge openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron-openvswitch openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3
  • openstack-neutron-macvtap-agent openstack 16.2 1:15.3.5-2.20210608154813.el8ost.3

red hat advisories RHSA-2021:3488RHSA-2021:3503RHSA-2021:3502RHSA-2021:3481

  • openstack-neutron OpenStack Cloud Crowbar 8, OpenStack Cloud 8, HPE Helion OpenStack 8 11.0.9~dev69-3.43.1
  • grafana OpenStack Cloud Crowbar 9, OpenStack Cloud 9 6.7.4-3.26.1
  • python-lxml OpenStack Cloud Crowbar 9, OpenStack Cloud 9 4.2.4-3.3.1
  • python-Pillow OpenStack Cloud Crowbar 9, OpenStack Cloud 9 5.2.0-3.17.1
  • ardana-barbican OpenStack Cloud 9 9.0+git.1644879908.8a641c1-3.13.1
  • rubygem-sinatra OpenStack Cloud Crowbar 9 1.4.6-4.3.1
  • openstack-cinder OpenStack Cloud Crowbar 9, OpenStack Cloud 9 13.0.10~dev24-3.34.2
  • openstack-ironic OpenStack Cloud Crowbar 9, OpenStack Cloud 9 11.1.5~dev18-3.28.2

suse advisories SUSE-SU-2022:1884-1SUSE-SU-2022:1729-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-40085 updated cvss 7.6

openstack-neutron: arbitrary dnsmasq reconfiguration via extra_dhcp_opts

  • Red Hat OpenStack Platform 10.0 python-neutron 9.4.1-56.el7ost, openstack-neutron 9.4.1-56.el7ost, python-neutron-tests 9.4.1-56.el7ost, openstack-neutron-ml2 9.4.1-56.el7ost, openstack-neutron-common 9.4.1-56.el7ost, openstack-neutron-rpc-server 9.4.1-56.el7ost, +5 more
    fixed: vendor fix RHSA-2021:3502
  • Red Hat OpenStack Platform 13.0 - ELS python-neutron 12.1.1-42.1.el7ost, openstack-neutron 12.1.1-42.1.el7ost, openstack-neutron-ml2 12.1.1-42.1.el7ost, openstack-neutron-common 12.1.1-42.1.el7ost, openstack-neutron-rpc-server 12.1.1-42.1.el7ost, openstack-neutron-linuxbridge 12.1.1-42.1.el7ost, +4 more Red Hat OpenStack Platform 13.0 for RHEL 7.6 EUS Server python-neutron 12.1.1-42.1.el7ost, openstack-neutron 12.1.1-42.1.el7ost, openstack-neutron-ml2 12.1.1-42.1.el7ost, openstack-neutron-common 12.1.1-42.1.el7ost, openstack-neutron-rpc-server 12.1.1-42.1.el7ost, openstack-neutron-linuxbridge 12.1.1-42.1.el7ost, +4 more
    fixed: vendor fix RHSA-2021:3503
  • Red Hat OpenStack Platform 16.1 python3-neutron 15.2.1-1.20210409073447.el8ost, openstack-neutron 15.2.1-1.20210409073447.el8ost, openstack-neutron-ml2 15.2.1-1.20210409073447.el8ost, openstack-neutron-common 15.2.1-1.20210409073447.el8ost, openstack-neutron-rpc-server 15.2.1-1.20210409073447.el8ost, openstack-neutron-linuxbridge 15.2.1-1.20210409073447.el8ost, +4 more
    fixed: vendor fix RHSA-2021:3481
  • Red Hat OpenStack Platform 16.2 python3-neutron 15.3.5-2.20210608154813.el8ost.3, openstack-neutron 15.3.5-2.20210608154813.el8ost.3, openstack-neutron-ml2 15.3.5-2.20210608154813.el8ost.3, openstack-neutron-common 15.3.5-2.20210608154813.el8ost.3, openstack-neutron-rpc-server 15.3.5-2.20210608154813.el8ost.3, openstack-neutron-linuxbridge 15.3.5-2.20210608154813.el8ost.3, +4 more
    fixed: vendor fix RHSA-2021:3488
  • Red Hat Integration Camel K 1 openstack-neutron Red Hat OpenStack Platform 17.1 python3-neutron, openstack-neutron, openstack-neutron-ml2, openstack-neutron-common, openstack-neutron-rpc-server, openstack-neutron-linuxbridge, +6 more Red Hat OpenStack Platform 18.0 openstack-neutron
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.87% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • launchpad.net https://launchpad.net/bugs/1939733 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:N/I:P/A:N
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
pypi neutron
<16.4.1
>=17.0.0, <17.2.1
>=18.0.0, <18.1.1
16.4.1
17.2.1
18.1.1

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.