CVE-2021-40085

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.8% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-08-31 · updated 2026-06-17

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.

Affected products

Debian Linux: 9.0, 10.0, 11.0
OpenStack Neutron: before 16.4.1; from 17.0.0 before 17.2.1; from 18.0.0 before 18.1.1 — fixed in 16.4.1, 17.2.1, 18.1.1

How to fix

Upgrade to a fixed version: OpenStack Neutron 16.4.1, 17.2.1, 18.1.1. Check the vendor advisory for mitigations.

References

http://www.openwall.com/lists/oss-security/2021/08/31/2
https://launchpad.net/bugs/1939733
https://lists.debian.org/debian-lts-announce/2021/10/msg00005.html
https://lists.debian.org/debian-lts-announce/2022/05/msg00038.html
https://security.openstack.org/ossa/OSSA-2021-005.html
https://www.debian.org/security/2021/dsa-4983
http://www.openwall.com/lists/oss-security/2021/08/31/2
https://launchpad.net/bugs/1939733
https://lists.debian.org/debian-lts-announce/2021/10/msg00005.html
https://lists.debian.org/debian-lts-announce/2022/05/msg00038.html
https://security.openstack.org/ossa/OSSA-2021-005.html
https://www.debian.org/security/2021/dsa-4983

Get alerted when CVE-2021-40085 or the next vulnerability affects your stack