Impact

Users of IPsec transparent encryption in Cilium may be vulnerable to cryptographic attacks that render the transparent encryption ineffective.

In particular, Cilium is vulnerable to the following attacks by a man-in-the-middle attacker:

- Chosen plaintext attacks - Key recovery attacks - Replay attacks

These attacks are possible due to an ESP sequence number collision when multiple nodes are configured with the same key. Fixed versions of Cilium use unique keys for each IPsec tunnel established between nodes, resolving all of the above attacks.

Important: After upgrading, users must perform a key rotation using the instructions here to ensure that they are no longer vulnerable to this issue. Please note that the key rotation instructions have recently been updated, and users must use the new instructions to properly establish secure IPsec tunnels. To validate that the new instructions have been followed properly, ensure that the IPsec Kubernetes secret contains a "+" sign.

Patches

All prior versions of Cilium that support IPsec transparent encryption (Cilium 1.4 onwards) are affected by this issue.

Patched versions:

- Cilium 1.15.3 - Cilium 1.14.9 - Cilium 1.13.14

Workarounds

There is no workaround to this issue. IPsec transparent encryption users are strongly encouraged to upgrade.

Acknowledgements

The Cilium community has worked together with members of Cure53 and Isovalent to prepare these mitigations. Special thanks to @NikAleksandrov and @pchaigno for their work on remediating the issue. Thanks to Marsh Ray, Senior Software Developer at Microsoft, for input and guidance on the fix.

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.

Impact

For Cilium users who: - Use Gateway API for Ingress for some services AND - Use LB-IPAM or BGP for LB Service implementation AND - Use network policies to block egress traffic from workloads in a namespace to workloads in other namespaces

Egress traffic from workloads covered by such network policies to LoadBalancers configured by Gateway resources will incorrectly be allowed.

LoadBalancer resources not deployed via a Gateway API configuration are not affected by this issue.

Patches

This issue was fixed by https://github.com/cilium/proxy/pull/1172.

This issue affects:

- Cilium v1.15 between v1.15.0 and v1.15.14 inclusive - Cilium v1.16 between v1.16.0 and v1.16.7 inclusive - Cilium v1.17 between v1.17.0 and v1.17.1 inclusive

This issue is fixed in:

- Cilium v1.15.15 - Cilium v1.16.8 - Cilium v1.17.2

Workarounds

A Clusterwide Cilium Network Policy can be used to work around this issue for users who are unable to upgrade. An outline of such a policy is provided below:

apiVersion: "cilium.io/v2" kind: CiliumClusterwideNetworkPolicy metadata: name: "workaround" spec: endpointSelector: matchExpressions: - key: reserved:ingress operator: Exists ingress: - fromEntities: - world

- The policy opens up connectivity from all locations outside the cluster into the Cilium Ingress Gateway. - The policy establishes a default deny for all other traffic towards the Cilium Ingress Gateway, including all in-cluster sources. - It is possible to tailor the policy to more narrowly allow inbound traffic while creating a default deny posture for traffic between namespaces. Users should edit the policy to bring it in line with the security requirements particular to their environments.

Acknowledgements

The Cilium community has worked together with members of the Isovalent team to prepare these mitigations. Special thanks to @jrajahalme for the fix.

For more information

If you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at security@cilium.io. This is a private mailing list for the Cilium security team, and your report will be treated as top priority.