CVE-2023-27594: Potential network policy bypass when routing IPv6 traffic

Impact

Under specific conditions, Cilium may misattribute the source IP address of traffic to a cluster, identifying external traffic as coming from the host on which Cilium is running. As a consequence, network policies for that cluster might be bypassed, depending on the specific network policies enabled. Only IPv6 traffic is impacted by this vulnerability.

This issue only manifests when:

• Cilium is routing IPv6 traffic, and
• Kube-proxy is used for service handling, and
• NodePorts are used to route traffic to pods.

IPv6 is disabled by default. Cilium's kube-proxy replacement feature is not affected by this vulnerability.

Patches

The problem has been fixed and is available on versions >=1.11.15, >=1.12.8, >=1.13.1

Workarounds

Disable IPv6 routing (IPv6 is disabled by default).

Acknowledgements

The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to Yusuke Suzuki for both highlighting and fixing the issue.

For more information

If you have any questions or comments about this advisory, please reach out on Slack.

As usual, if you think you found a related vulnerability, we strongly encourage you to report security vulnerabilities to our private security mailing list: security@cilium.io - first, before disclosing them in any public forums. This is a private mailing list where only members of the Cilium internal security team are subscribed to, and is treated as top priority.