CVE-2020-8563 in Kubernetes
Summary
by MITRE • 12/08/2020
In Kubernetes clusters using VSphere as a cloud provider, with a logging level set to 4 or above, VSphere cloud credentials will be leaked in the cloud controller manager's log. This affects < v1.19.3.
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Analysis
by VulDB Data Team • 12/13/2020
The vulnerability described in CVE-2020-8563 represents a critical information disclosure flaw within Kubernetes clusters that utilize VMware vSphere as their cloud provider infrastructure. This security weakness specifically manifests when clusters are configured with logging verbosity levels set to 4 or higher, creating an unintended exposure of sensitive authentication credentials. The issue affects Kubernetes versions prior to 1.19.3, making it a significant concern for organizations running older cluster deployments that have not yet been updated to mitigate this risk.
The technical mechanism behind this vulnerability stems from the improper handling of sensitive data within the cloud controller manager component of Kubernetes. When the logging level reaches verbosity 4 or above, the system inadvertently includes vSphere cloud provider credentials in log output streams, effectively writing authentication tokens and credential information to log files that should remain secure. This occurs because the logging implementation fails to sanitize or redact sensitive parameters that are passed to the cloud provider interface during operational activities. The vulnerability is classified under CWE-209, which specifically addresses "Information Exposure Through an Error Message," though it manifests more broadly as credential leakage through log output rather than traditional error message exposure.
The operational impact of this vulnerability extends beyond simple credential exposure, as it provides attackers with direct access to vSphere cloud provider authentication mechanisms that can be leveraged for unauthorized access to cloud resources. An attacker who gains access to these logs can extract the vSphere credentials and potentially use them to compromise the underlying cloud infrastructure, escalate privileges within the vSphere environment, or access other systems that rely on the same authentication context. The risk is particularly elevated in environments where logging verbosity is set to high levels for troubleshooting purposes, as this configuration is common in production environments where detailed operational information is required for monitoring and debugging activities. This vulnerability directly aligns with ATT&CK technique T1567.002, which covers "Exfiltration Over Web Service" through credential access and persistence mechanisms.
Organizations affected by this vulnerability should immediately implement several mitigation strategies to protect their Kubernetes environments. The primary recommendation involves upgrading affected Kubernetes clusters to version 1.19.3 or later, where the logging behavior has been corrected to prevent credential exposure. Additionally, administrators should review and adjust logging verbosity levels to the minimum required for operational needs, avoiding unnecessary high-verbosity settings that could expose sensitive information. Implementing log access controls and monitoring for unusual log file access patterns can help detect potential credential theft attempts. Security teams should also conduct comprehensive audits of their vSphere credential management practices, ensuring that credentials are rotated regularly and that access controls are properly configured. The mitigation approach should include deploying centralized logging solutions with proper log sanitization capabilities and implementing network segmentation to limit access to sensitive log files, thereby reducing the attack surface and potential impact of credential exposure.