The kubectl cp command allows copying files between containers and the user machine. To copy files from a container, Kubernetes creates a tar inside the container, copies it over the network, and kubectl unpacks it on the user’s machine. If the tar binary in the container is malicious, it could run any code and output unexpected, malicious results. An attacker could use this to write files to any path on the user’s machine when kubectl cp is called, limited only by the system permissions of the local user. The untar function can both create and follow symbolic links. The issue is resolved in kubectl v1.11.9, v1.12.7, v1.13.5, and v1.14.0.

A third issue was discovered with the Kubernetes kubectl cp command that could enable a directory traversal such that a malicious container could replace or create files on a user’s workstation. The vulnerability is a client-side defect and requires user interaction to be exploited.

This vulnerability allows a malicious container to cause a file to be created or replaced on the client computer when the client uses the kubectl cp operation. The vulnerability is a client-side defect and requires user interaction to be exploited.

Upstream Issue:

https://github.com/kubernetes/kubernetes/issues/80984

External References:

https://groups.google.com/forum/#!topic/kubernetes-security-discuss/Vf31dXp0EJc

A denial of service vulnerability was found in the Kubernetes API server. A remote user, with authorization to apply patches, could exploit this via crafted JSON input, causing excessive consumption of resources and subsequent denial of service.