Skipper Ingress Controller Allows Unauthorized Access to Internal Services via ExternalName in github.com/zalando/skipper

Open Source Vulnerabilities CVE-2026-24470

Skipper is an HTTP router and reverse proxy for service composition. Prior to version 0.24.0, when running Skipper as an Ingress controller, users with permissions to create an Ingress and a Service of type ExternalName can create routes that enable them to use Skipper's network access to reach internal services. Version 0.24.0 disables Kubernetes ExternalName by default. As a workaround, developers can allow list targets of an ExternalName and allow list via regular expressions.

Open Source Vulnerabilities GO-2026-4378

Skipper Ingress Controller Allows Unauthorized Access to Internal Services via ExternalName in github.com/zalando/skipper

Open Source Vulnerabilities GHSA-mxxc-p822-2hx9

### Impact When running Skipper as an Ingress controller, users with permissions to create an Ingress and a Service of type ExternalName can create routes that enable them to use Skipper's network access to reach internal services. ### Patches https://github.com/zalando/skipper/releases/tag/v0.24.0 disables Kubernetes ExternalName by default. ### Workarounds Developers can allow list targets of an ExternalName by using `-kubernetes-only-allowed-external-names=true` and allow list via regular expressions `-kubernetes-allowed-external-name '^[a-z][a-z0-9-.]+[.].allowed.example$'` ### References https://kubernetes.io/docs/concepts/services-networking/service/#externalname