A security issue was discovered in Kubernetes where actors that control the responses of MutatingWebhookConfiguration or ValidatingWebhookConfiguration requests are able to redirect kube-apiserver requests to private networks of the apiserver. If that user can view kube-apiserver logs when the log level is set to 10, they can view the redirected responses and headers in the logs.
The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product’s control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Kubernetes | Kubernetes | 1.20.11 (including) | 1.20.11 (including) |
| Kubernetes | Kubernetes | 1.21.5 (including) | 1.21.5 (including) |
| Kubernetes | Kubernetes | 1.22.2 (including) | 1.22.2 (including) |
| Kubernetes | Ubuntu | hirsute | * |
| Kubernetes | Ubuntu | impish | * |
| Kubernetes | Ubuntu | kinetic | * |
| Kubernetes | Ubuntu | lunar | * |
| Kubernetes | Ubuntu | mantic | * |
If an attacker cannot directly contact a target, but the product has access to the target, then the attacker can send a request to the product and have it be forwarded to the target. The request would appear to be coming from the product’s system, not the attacker’s system. As a result, the attacker can bypass access controls (such as firewalls) or hide the source of malicious requests, since the requests would not be coming directly from the attacker. Since proxy functionality and message-forwarding often serve a legitimate purpose, this issue only becomes a vulnerability when: