Podman Vulnerable to Symlink Traversal Attack

Summary

A vulnerability was found in Podman, Buildah, and CRI-O. A symlink traversal vulnerability in the containers/storage library can cause Podman, Buildah, and CRI-O to hang and result in a denial of service via OOM kill when running a malicious image using an automatically assigned user namespace (`--userns=auto` in Podman and Buildah). The containers/storage library will read /etc/passwd inside the container, but does not properly validate if that file is a symlink, which can be used to cause the library to read an arbitrary file on the host.