CVE-2019-3779 in Container Runtime
Summary
by MITRE
Cloud Foundry Container Runtime, versions prior to 0.29.0, deploys Kubernetes clusters utilize the same CA (Certificate Authority) to sign and trust certs for ETCD as used by the Kubernetes API. This could allow a user authenticated with a cluster to request a signed certificate leveraging the Kubernetes CSR capability to obtain a credential that could escalate privilege access to ETCD.
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Analysis
by VulDB Data Team • 07/31/2023
The Cloud Foundry Container Runtime vulnerability CVE-2019-3779 represents a critical security flaw in Kubernetes cluster deployments that leverages certificate authority misconfiguration to enable privilege escalation. This vulnerability affects versions prior to 029.0 of the Cloud Foundry Container Runtime and specifically targets the certificate management infrastructure that governs trust relationships within Kubernetes clusters. The flaw stems from the improper separation of certificate authority responsibilities between different cluster components, creating an exploitable gap in the security architecture that allows authenticated users to manipulate certificate signing processes.
The technical implementation of this vulnerability exploits the Kubernetes Certificate Signing Request (CSR) mechanism, which is designed to allow cluster components to request and receive certificates from the Kubernetes API server. In the affected versions, the same certificate authority that validates and signs certificates for the Kubernetes API server also serves as the authority for signing certificates used by etcd, the distributed database that stores cluster state information. This architectural overlap creates a scenario where an authenticated user with legitimate cluster access can submit a CSR request that leverages the existing trust relationship to obtain a certificate that grants access to etcd components.
The operational impact of this vulnerability extends beyond simple privilege escalation, as etcd contains critical cluster configuration data and state information that directly influences the entire Kubernetes environment. When an attacker successfully obtains an etcd-access certificate through this mechanism, they gain the ability to read, modify, or delete sensitive cluster data including pod configurations, service definitions, and namespace permissions. This access level essentially provides the attacker with complete control over the cluster's operational state and can lead to data breaches, service disruption, or further lateral movement within the infrastructure. The vulnerability particularly affects environments where cluster users have legitimate access to the Kubernetes API but should not have administrative access to etcd components.
The security implications of CVE-2019-3779 align with CWE-310, which addresses cryptographic vulnerabilities related to improper certificate handling and trust management. This weakness specifically manifests as a failure in certificate authority separation, creating an attack surface that violates fundamental security principles of least privilege and defense in depth. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1552.001, which covers "Unsecured Credentials" and specifically targets credential access through legitimate system access. The vulnerability demonstrates how improper certificate authority management can be exploited to bypass normal access controls and escalate privileges within containerized environments. Organizations should implement immediate mitigations including upgrading to Cloud Foundry Container Runtime version 0.29.0 or later, which properly separates certificate authority responsibilities between Kubernetes API and etcd components, and establishing monitoring for unusual certificate signing requests within the cluster infrastructure.
The remediation approach for this vulnerability requires a multi-layered strategy that addresses both the immediate technical flaw and broader infrastructure security practices. System administrators must first upgrade to the patched version of Cloud Foundry Container Runtime that implements proper certificate authority separation, ensuring that distinct certificate authorities are used for Kubernetes API components and etcd access. Additionally, organizations should implement enhanced monitoring of certificate signing activities through cluster logging and alerting systems that can detect anomalous CSR requests. The vulnerability highlights the importance of maintaining proper separation of duties and trust boundaries within container orchestration platforms, where the compromise of one component should not automatically grant access to other critical system components. Regular security assessments of certificate management practices and access control policies should be conducted to prevent similar configuration errors that could create similar privilege escalation opportunities in other infrastructure components.