CVE-2020-8564 in Kubernetes
Summary
by MITRE • 12/08/2020
In Kubernetes clusters using a logging level of at least 4, processing a malformed docker config file will result in the contents of the docker config file being leaked, which can include pull secrets or other registry credentials. This affects < v1.19.3, < v1.18.10, < v1.17.13.
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Analysis
by VulDB Data Team • 12/13/2020
The vulnerability described in CVE-2020-8564 represents a critical information disclosure flaw within Kubernetes clusters that manifests when the logging level is configured to at least level 4. This issue specifically targets the handling of malformed docker configuration files within the Kubernetes environment, creating a scenario where sensitive credential data can be inadvertently exposed through cluster logs. The vulnerability affects multiple Kubernetes versions including those prior to v1.19.3, v1.18.10, and v1.17.13, indicating a widespread impact across several major release branches. The root cause lies in the improper validation and processing of docker configuration files that contain malformed entries, which triggers an error handling mechanism that logs the contents of these configuration files.
The technical implementation of this vulnerability stems from the way Kubernetes processes docker configuration files during container image pull operations. When a malformed docker config file is encountered, the system's logging mechanism at level 4 or higher attempts to provide detailed debugging information about the error. This logging process inadvertently includes the complete contents of the docker config file, which typically contains registry credentials, pull secrets, and other sensitive authentication information. The flaw is categorized under CWE-200 Information Exposure, where sensitive data is disclosed through improper error handling. The vulnerability aligns with ATT&CK technique T1552.001 Credential Access: Credentials In Files, as it exposes authentication credentials that are stored in configuration files through improper logging practices.
The operational impact of this vulnerability is severe for organizations running Kubernetes clusters with elevated logging levels, particularly in production environments where detailed debugging information is enabled. Attackers who gain access to cluster logs or monitoring systems could extract sensitive registry credentials, pull secrets, and authentication tokens that would allow them to pull unauthorized container images from private registries. This exposure could lead to unauthorized access to container repositories, potential code execution through malicious image pulls, and broader compromise of containerized applications. The vulnerability particularly affects environments where security best practices include enabling detailed logging for troubleshooting purposes, creating a dangerous intersection between operational necessity and security risk.
Mitigation strategies for CVE-2020-8564 should focus on immediate version upgrades to patched Kubernetes releases, specifically ensuring all clusters are updated to v1.19.3, v1.18.10, or v1.17.13 respectively. Organizations should also implement strict log filtering and monitoring to prevent sensitive information from being logged, particularly by configuring logging levels appropriately and implementing log sanitization procedures. The remediation process should include reviewing and updating docker configuration files to ensure they are properly formatted and validated before deployment. Additionally, organizations should establish comprehensive monitoring for credential exposure in log files and implement automated scanning tools to detect sensitive information in cluster logs. Security teams should also consider implementing network segmentation and access controls to limit exposure of logging systems and ensure that only authorized personnel have access to detailed cluster logs containing potentially sensitive information.