CVE-2026-33726: Cilium L7 proxy may bypass Kubernetes NetworkPolicy for same-node traffic
Impact
Ingress Network Policies are not enforced for traffic from pods to L7 Services (Envoy, GAMMA) with a local backend on the same node, when Per-Endpoint Routing is enabled and BPF Host Routing is disabled.
Per-Endpoint Routing is disabled by default, but is automatically enabled in deployments using cloud IPAM, including Cilium ENI on EKS (eni.enabled), AlibabaCloud ENI (alibabacloud.enabled), Azure IPAM (azure.enabled, but not AKS BYOCNI), and some GKE deployments (gke.enabled; managed offerings such as GKE Dataplane V2 may use different defaults). It is typically not enabled in tunneled deployments, and chaining deployments are not affected. In practice, Amazon EKS with Cilium ENI mode is likely the most common affected environment.
Patches
This issue was fixed by #44693.
This issue affects:
Cilium v1.19 between v1.19.0 and v1.19.1 inclusive Cilium v1.18 between v1.18.0 and v1.18.7 inclusive All versions of Cilium prior to v1.17.13
This issue is fixed in:
Cilium v1.19.2 Cilium v1.18.8 Cilium v1.17.14
Workarounds
Disclaimer: There is currently no officially verified or comprehensive workaround for this issue. The only option would be to disable per-endpoint routes, but this will likely cause disruptions to ongoing connections, and potential conflicts if running in cloud providers.
Acknowledgements
The Cilium community has worked together with members of the Northflank and Isovalent teams to prepare these mitigations. Cilium thanks @sudeephb and @Champ-Goblem for reporting the issue and to @smagnani96 and @julianwiedmann for helping with the resolution.
For more information
Anyone who believes a vulnerability affecting Cilium has been found is strongly encouraged to report it to the security mailing list at security@cilium.io. This is a private mailing list for the Cilium security team, and any such report will be treated as top priority. Please also address any comments or questions on this advisory to the same mailing list.
Other sources
Cilium is a networking, observability, and security solution with an eBPF-based dataplane. Prior to versions 1.17.14, 1.18.8, and 1.19.2, Ingress Network Policies are not enforced for traffic from pods to L7 Services (Envoy, GAMMA) with a local backend on the same node, when Per-Endpoint Routing is enabled and BPF Host Routing is disabled. Per-Endpoint Routing is disabled by default, but is automatically enabled in deployments using cloud IPAM, including Cilium ENI on EKS (eni.enabled), AlibabaCloud ENI (alibabacloud.enabled), Azure IPAM (azure.enabled, but not AKS BYOCNI), and some GKE deployments (gke.enabled; managed offerings such as GKE Dataplane V2 may use different defaults). It is typically not enabled in tunneled deployments, and chaining deployments are not affected. In practice, Amazon EKS with Cilium ENI mode is likely the most common affected environment. Versions 1.17.14, 1.18.8, and 1.19.2 contain a patch. There is currently no officially verified or comprehensive workaround for this issue. The only option would be to disable per-endpoint routes, but this will likely cause disruptions to ongoing connections, and potential conflicts if running in cloud providers.
— MITRE
Affected Software
Remediation
Patch Available
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33726?
CVE-2026-33726 is classified as a medium severity vulnerability due to the potential for unauthorized access and exposure of L7 service traffic.
How do I fix CVE-2026-33726?
To resolve CVE-2026-33726, upgrade to Cilium version 1.19.2, 1.18.8, or ensure you are using a version prior to 1.17.14.
What types of systems are affected by CVE-2026-33726?
CVE-2026-33726 affects systems using Cilium network policies for Kubernetes with local backends on the same node.
What impact does CVE-2026-33726 have on network security?
CVE-2026-33726 may result in the enforcement failure of ingress network policies, leading to potential traffic interception and data leaks.
Is there a workaround for CVE-2026-33726 if I cannot upgrade?
There are no documented workarounds for CVE-2026-33726; an upgrade is the recommended mitigation.