CVE-2020-8561 Explained : Impact and Mitigation

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.

Understanding CVE-2020-8561

This CVE involves a vulnerability in Kubernetes that allows actors to redirect kube-apiserver requests to private networks, potentially exposing sensitive information.

What is CVE-2020-8561?

CVE-2020-8561 is a security issue in Kubernetes that enables actors to manipulate webhook responses, leading to the redirection of kube-apiserver requests to private networks.

The Impact of CVE-2020-8561

The vulnerability can allow unauthorized users to access redirected responses and headers in kube-apiserver logs, potentially compromising the security and confidentiality of the system.

Technical Details of CVE-2020-8561

This section provides detailed technical information about the CVE.

Vulnerability Description

The vulnerability allows actors to control responses of webhook requests, redirecting kube-apiserver requests to private networks.

Affected Systems and Versions

Kubernetes versions 1.20.11 and below are affected.
Versions 1.21.5 and 1.22.2 are also impacted.

Exploitation Mechanism

Actors manipulate MutatingWebhookConfiguration or ValidatingWebhookConfiguration responses to redirect kube-apiserver requests.

Mitigation and Prevention

Protect your systems from CVE-2020-8561 with the following steps:

Immediate Steps to Take

Update Kubernetes to versions that have patches addressing the vulnerability.
Monitor kube-apiserver logs for any suspicious activity.

Long-Term Security Practices

Implement strict access controls to limit who can view kube-apiserver logs.
Regularly audit and review webhook configurations for any unauthorized changes.

Patching and Updates

Apply security patches provided by Kubernetes promptly to mitigate the vulnerability.