Certificate Signing Request Validation Bypass in ManagedCluster Import Controller

Executive Summary

This vulnerability is in the managedcluster-import-controller where the CSR auto-approval logic fails to properly validate incoming Certificate Signing Requests. It does not check the signer name or decode the PEM-encoded x509 CSR, allowing a privileged service account on a spoke cluster to submit a malicious CSR. Exploitation can lead to privilege escalation and unauthorized administrative access to the hub cluster.

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Detection Guidance

Detecting this vulnerability requires monitoring Certificate Signing Requests (CSRs) and validating their signer names and PEM-encoded x509 content. Check logs for unusual CSR submissions from spoke clusters and verify approval processes. No specific commands are provided in the context.

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Impact Analysis

If exploited, this vulnerability allows an attacker with access to a spoke cluster to gain administrative credentials on the hub cluster. This could lead to unauthorized control over the entire cluster environment, data breaches, or further lateral movement within the infrastructure.

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Compliance Impact

This vulnerability could potentially impact compliance with standards like GDPR and HIPAA by enabling unauthorized privilege escalation. If exploited, an attacker could gain administrative credentials on the hub cluster, potentially leading to unauthorized access to sensitive data. This may violate data protection requirements under GDPR (e.g., unauthorized access to personal data) and HIPAA (e.g., unauthorized access to protected health information).

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Mitigation Strategies

Disable automatic CSR approval in the managedcluster-import-controller and manually review all incoming CSRs before approval. Restrict privileges of service accounts on spoke clusters to prevent unauthorized CSR submissions.

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