# CVE-2021-40085: OpenStack Neutron vulnerable to authenticated attackers reconfiguring dnsmasq via crafted extra_dhcp_opts value

Source: https://junglewise.ai/threats/cve-2021-40085-openstack-neutron-vulnerable-to-authenticated-attackers  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-08-31  
License: CC BY 4.0 with a link back

CVE-2021-40085 · Severity: low · CVSS 3.1 · Published 2021-08-31

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.

Technologies: [neutron (PyPI)](https://junglewise.ai/threats/technologies/pypi-neutron). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-40085 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-40085 being exploited in the wild.

**How severe is CVE-2021-40085?** Low severity, with a CVSS score of 3.1, published 31 August 2021.

**Which products and versions are affected?** neutron (PyPI) ECOSYSTEM:introduced=0,fixed=16.4.1, ECOSYSTEM:introduced=0,fixed=16.4.1,introduced=17.0.0,fixed=17.2.1,introduced=18.0.0,fixed=18.1.1.

**Is there a fix for CVE-2021-40085?** Yes. neutron (PyPI): upgrade to 16.4.1, 18.1.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-40085?** Check whether you run neutron (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- neutron (PyPI): upgrade to 16.4.1, 18.1.1 or later

  ```sh
  pip install "neutron>=18.1.1"
  ```


## Affected products

- neutron (PyPI) ECOSYSTEM:introduced=0,fixed=16.4.1, ECOSYSTEM:introduced=0,fixed=16.4.1,introduced=17.0.0,fixed=17.2.1,introduced=18.0.0,fixed=18.1.1

## Identifiers

- CVE-2021-40085
- GHSA-fh73-gjvg-349c
- PYSEC-2021-361

## Related threats

- [PYSEC-2026-1693 - OpenStack Neutron can use an incorrect ID during policy enforcement](https://junglewise.ai/threats/cve-2024-53916-openstack-neutron-can-use-an-incorrect-id-during-policy)
- [PYSEC-2026-1694 - Denial of service in neutron](https://junglewise.ai/threats/cve-2023-3637-denial-of-service-in-neutron)
- [PYSEC-2026-855 - openstack-neutron uncontrolled resource consumption flaw](https://junglewise.ai/threats/cve-2022-3277-openstack-neutron-uncontrolled-resource-consumption-flaw)
- [PYSEC-2026-851 - OpenStack Neutron Improper Authentication vulnerability](https://junglewise.ai/threats/cve-2014-0056-openstack-neutron-improper-authentication-vulnerability)
- [PYSEC-2026-853 - OpenStack Neutron Race condition vulnerability](https://junglewise.ai/threats/cve-2015-5240-openstack-neutron-race-condition-vulnerability)