CVE-2020-25655 in Advanced Cluster Management for Kubernetes
Summary
by MITRE • 11/09/2020
An issue was discovered in ManagedClusterView API, that could allow secrets to be disclosed to users without the correct permissions. Views created for an admin user would be made available for a short time to users with only view permission. In this short time window the user with view permission could read cluster secrets that should only be disclosed to admin users.
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Analysis
by VulDB Data Team • 12/04/2020
The vulnerability identified as CVE-2020-25655 resides within the ManagedClusterView API component of a Kubernetes-based cluster management system, representing a critical access control flaw that undermines the fundamental security principles of privilege separation and least privilege enforcement. This issue manifests as a temporal window vulnerability where administrative privileges are temporarily leaked to users with only view-level permissions, creating an exploitable gap in the authorization mechanism that should prevent unauthorized information disclosure. The flaw specifically affects the cluster view management functionality where the system fails to properly enforce access controls during the brief period when views are being processed or updated, allowing malicious actors with minimal permissions to intercept sensitive cluster information.
The technical implementation of this vulnerability stems from inadequate synchronization and access control mechanisms within the ManagedClusterView API. When an administrator creates or modifies a view, the system does not immediately revoke access permissions for lower-privileged users, creating a race condition where the view becomes temporarily accessible to unauthorized users. This temporal inconsistency in privilege enforcement violates the core security principle that access control decisions should be consistently enforced at all times, not just during specific operational phases. The vulnerability can be classified under CWE-284 (Improper Access Control) and aligns with ATT&CK technique T1078 (Valid Accounts) as it exploits legitimate user accounts to gain unauthorized access to sensitive information. The underlying flaw likely involves improper handling of view lifecycle management, where access tokens or permissions are not properly invalidated or re-evaluated during the transition from administrative to restricted access states.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates a window of opportunity for attackers to access potentially sensitive cluster secrets, credentials, and configuration data that should remain restricted to administrative users only. This exposure could enable attackers to escalate their privileges within the cluster, potentially leading to full compromise of the containerized environment. The short time window mentioned in the description suggests that this is not a persistent vulnerability but rather a timing-dependent flaw that requires precise exploitation conditions. However, the temporal nature of this vulnerability makes it particularly dangerous as automated scanning tools or repeated attempts could potentially exploit the window before access controls are properly enforced. Organizations using affected systems face significant risk of credential theft, data exfiltration, and potential lateral movement within their cluster environments, particularly in multi-tenant deployments where multiple users with varying permission levels share the same infrastructure.
Mitigation strategies for CVE-2020-25655 should focus on implementing immediate patching of the ManagedClusterView API component to correct the access control implementation and eliminate the temporal window where unauthorized access occurs. Organizations should enforce stricter access control policies and implement proper view lifecycle management that ensures immediate revocation of access permissions when administrative operations occur. The solution involves implementing robust synchronization mechanisms that prevent any unauthorized access during the transition phases of view creation or modification, utilizing atomic operations or proper locking mechanisms to ensure that access control decisions are consistently enforced throughout the entire process. Additionally, system administrators should implement monitoring and alerting for unauthorized access attempts and consider implementing role-based access control improvements that enforce more granular permissions. The remediation process should include thorough testing to ensure that the fix does not introduce performance degradation or operational issues while maintaining the security posture of the cluster management system. Organizations should also review their broader access control policies to identify similar temporal window vulnerabilities in other components of their Kubernetes infrastructure.