No exploitation reportedFix available

CVE-2021-40085

Q: Is CVE-2021-40085 actively exploited?

Active exploitation of CVE-2021-40085 has not been confirmed. Its EPSS score was 1.8% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-40085?

CVE-2021-40085 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.

No exploitation reported by the sources we read.

Published2021-08-31

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2021-08-3118:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-40085?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-40085?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Debian debian linux

Branch	Affected	Fixed in	Source
9.0	= 9.0	no fix published	NVD
10.0	= 10.0	no fix published	NVD
11.0	= 11.0	no fix published	NVD

Openstack neutron

Branch	Affected	Fixed in	Source
18.x	≥ 18.0.0, < 18.1.1	18.1.1	NVD · OSV
17.x	≥ 17.0.0, < 17.2.1	17.2.1	NVD · OSV
16.4	< 16.4.1	16.4.1	NVD · OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

CVE-2021-40085 Red Hat Product Security56 products fixed
openstack-neutron: arbitrary dnsmasq reconfiguration via extra_dhcp_opts
RHSA-2021:3488 Red Hat Product Security11 products fixed
Red Hat Security Advisory: Red Hat OpenStack Platform 16.2 (openstack-neutron) security update
RHSA-2021:3503 Red Hat Product Security22 products fixed
Red Hat Security Advisory: Red Hat OpenStack Platform 13.0 (openstack-neutron) security update
RHSA-2021:3502 Red Hat Product Security12 products fixed
Red Hat Security Advisory: Red Hat OpenStack Platform 10.0 (openstack-neutron) security update
RHSA-2021:3481 Red Hat Product Security11 products fixed
Red Hat Security Advisory: Red Hat OpenStack Platform 16.1 (openstack-neutron) security update

Full record on NVD

Fix

Vendor fix Red Hat Product Security RHSA-2021:3488 · 11 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Workaround from the vendor Red Hat Product Security RHSA-2021:3488 · 11 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Advisories and patches

www.openwall.comPatch
security.openstack.orgPatch · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.16.5read 2026-10-23
NVDCVSS 2.04read 2026-10-23
FIRST EPSSEPSS score1.8 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Published: 2021-08-31
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-40085?

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.

Is CVE-2021-40085 actively exploited?

Active exploitation of CVE-2021-40085 has not been confirmed. Its EPSS score was 1.8% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-40085?

CVE-2021-40085 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.

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