CVE-2020-8565 in Kubernetes
Summary
by MITRE • 12/08/2020
In Kubernetes, if the logging level is set to at least 9, authorization and bearer tokens will be written to log files. This can occur both in API server logs and client tool output like kubectl. This affects
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Analysis
by VulDB Data Team • 03/28/2025
The vulnerability identified as CVE-2020-8565 represents a critical security flaw in the Kubernetes authorization framework that exposes sensitive authentication tokens through logging mechanisms. This issue specifically manifests when the Kubernetes API server operates with a logging verbosity level of 9 or higher, where the system begins to log authorization decisions and bearer tokens in plaintext format. The exposure occurs within both the API server's operational logs and client tool outputs including kubectl commands, creating multiple attack vectors for malicious actors seeking to compromise cluster security.
The technical implementation of this vulnerability stems from improper handling of sensitive data within the logging subsystem of Kubernetes components. When logging verbosity reaches level 9, the system's authorization module begins to include full bearer tokens and authorization context in log entries, which are typically stored in accessible file systems. This flaw directly violates security best practices for handling authentication credentials and represents a violation of the principle of least privilege. The vulnerability can be categorized under CWE-532, which specifically addresses "Information Exposure Through Log Files" and aligns with ATT&CK technique T1567.002 for "Use of Network Protocols for Command and Control" as attackers can leverage these exposed tokens to gain unauthorized access to cluster resources.
The operational impact of this vulnerability is severe and far-reaching across Kubernetes deployments. An attacker who gains access to system logs or can execute commands that produce log output at verbosity level 9 can immediately obtain valid bearer tokens for cluster access. This compromises the entire authentication infrastructure, allowing unauthorized users to perform administrative actions, access sensitive workloads, and potentially escalate privileges within the cluster. The exposure affects both the API server and client tools, meaning that any user with access to log files or the ability to execute kubectl commands at elevated verbosity levels could inadvertently expose tokens. This vulnerability particularly impacts environments where logging is configured for debugging purposes or where multiple administrators have access to system logs, creating a significant attack surface that can be exploited across various threat scenarios.
Mitigation strategies for CVE-2020-8565 require immediate configuration adjustments to prevent token exposure while maintaining operational visibility. Organizations should reduce logging verbosity levels to 8 or lower to prevent token logging, implement strict access controls on log files to ensure only authorized personnel can view them, and establish monitoring for elevated logging levels that might expose sensitive information. Additionally, implementing log rotation with secure deletion policies, deploying centralized logging solutions with proper filtering, and regularly auditing logging configurations can help prevent future occurrences. The recommended approach aligns with security frameworks such as the NIST Cybersecurity Framework and follows the principle of defense in depth as outlined in the MITRE ATT&CK matrix, particularly addressing the persistence and privilege escalation techniques that could leverage such exposed tokens. Organizations should also consider implementing token rotation policies and multi-factor authentication mechanisms to reduce the impact of any potential token compromise.