CVE-2026-113951 in Container
Summary
by MITRE • 10/24/2026
If an attacker can write to the filesystem of a container k8s cluster container, they can plant an exec credential plugin in /etc/kubernetes/admin.conf. kubectl will run that plugin as the macOS host user the next time someone pulls the cluster's kubeconfig onto the host with container k8s write-config or create and then runs kubectl against it — turning filesystem access inside an untrusted Linux container into arbitrary command execution on the host. This vulnerability is addressed in Container version 1.5.0.
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Analysis
by VulDB Data Team • 10/24/2026
The described vulnerability represents a critical escalation of privilege that bridges the gap between isolated container environments and the underlying macOS host system, fundamentally undermining the security boundaries established by Kubernetes and containerization technologies. The core technical flaw lies in the interaction between the kubeconfig file format, specifically its support for exec credential plugins, and the execution context of the kubectl command-line tool on the host machine. When a user retrieves cluster configuration data using commands such as write-config or create within an untrusted Linux container environment that possesses filesystem write access, they inadvertently facilitate the injection of malicious code into the administrative configuration file located at /etc/kubernetes/admin.conf. This action transforms what appears to be simple read-write access inside a sandboxed container into arbitrary command execution on the host operating system with elevated privileges.
The mechanism relies heavily on how kubectl handles authentication and credential management. Modern Kubernetes configurations often utilize exec plugins for dynamic token generation or certificate rotation, allowing tools like AWS IAM authenticators or Azure AD plugins to execute external binaries during API requests. If an attacker can modify the admin.conf file within the container's filesystem before it is copied out, they can insert a malicious executable script or binary disguised as a legitimate credential plugin. When this configuration is subsequently pulled onto the macOS host and used with kubectl, the tool parses the config, identifies the exec command specified in the authentication section, and executes it directly under the context of the user running the terminal session on the Mac. This results in immediate arbitrary code execution without requiring additional privilege escalation steps or exploiting separate kernel vulnerabilities.
From an operational impact perspective, this vulnerability allows a malicious actor who has gained foothold inside any container within the cluster to achieve full control over the host machine where the kubeconfig is utilized. Since the admin.conf file typically contains credentials with cluster-admin level permissions, compromising it grants access not only to the local macOS environment but potentially to all resources managed by that Kubernetes cluster if the same config is used for administrative purposes across multiple nodes or management interfaces. This effectively nullifies the isolation guarantees provided by container runtimes and orchestration platforms, turning a lateral movement opportunity inside the cluster into a complete system compromise of the developer's workstation or CI/CD runner host.
This vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command, as it involves the injection and subsequent execution of arbitrary commands through configuration files that are interpreted by trusted binaries. It also maps to MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically leveraging legitimate system tools like kubectl to execute malicious payloads. Furthermore, it relates to CWE-269 Improper Privilege Management because the executed code inherits the high-level privileges of the host user who invoked kubectl, often an administrator or developer with broad access rights. The attack vector is classified as local due to the requirement for initial filesystem write access within the container, but its impact extends significantly beyond that boundary into the host environment.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is upgrading Container version 1.5.0 or later, which addresses this specific flaw in how configuration files are handled during export operations. In environments where updating is not immediately feasible, administrators should restrict filesystem write permissions within containers to the absolute minimum required for application functionality, adhering to the principle of least privilege. Additionally, organizations should implement strict image scanning and runtime security monitoring to detect unauthorized modifications to sensitive paths like /etc/kubernetes/admin.conf. It is also advisable to use separate kubeconfig files with limited scopes for different tasks rather than relying on a single admin config file that carries excessive privileges across all contexts. Finally, enabling audit logging for kubectl executions can help in detecting anomalous behavior indicative of credential plugin abuse or unauthorized configuration changes.