containerd CRI plugin: Insecure handling of image volumes

### Impact

A bug was found in containerd where containers launched through containerd’s CRI implementation with a specially-crafted image configuration could gain access to read-only copies of arbitrary files and directories on the host. This may bypass any policy-based enforcement on container setup (including a Kubernetes Pod Security Policy) and expose potentially sensitive information. Kubernetes and crictl can both be configured to use containerd’s CRI implementation.

### Patches

This bug has been fixed in containerd 1.6.1, 1.5.10 and 1.4.13. Users should update to these versions to resolve the issue.

### Workarounds

Ensure that only trusted images are used.

### Credits

The containerd project would like to thank Felix Wilhelm of Google Project Zero for responsibly disclosing this issue in accordance with the [containerd security policy](https://github.com/containerd/project/blob/main/SECURITY.md).

### For more information

If you have any questions or comments about this advisory:

* Open an issue in [containerd](https://github.com/containerd/containerd/issues/new/choose) * Email us at [security@containerd.io](mailto:security@containerd.io)