Cilium East-west traffic not subject to egress policy enforcement for requests via Gateway API load balancers

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 [email protected]. This is a private mailing list for the Cilium security team, and your report will be treated as top priority.