containerd is an open source container runtime. A bug was found in containerd prior to versions 1.6.18 and 1.5.18 where supplementary groups are not set up properly inside a container. If an attacker has direct access to a container and manipulates their supplementary group access, they may be able to use supplementary group access to bypass primary group restrictions in some cases, potentially gaining access to sensitive information or gaining the ability to execute code in that container. Downstream applications that use the containerd client library may be affected as well. This bug has been fixed in containerd v1.6.18 and v.1.5.18. Users should update to these versions and recreate containers to resolve this issue. Users who rely on a downstream application that uses containerd's client library should check that application for a separate advisory and instructions. As a workaround, ensure that the `"USER $USERNAME"` Dockerfile instruction is not used. Instead, set the container entrypoint to a value similar to `ENTRYPOINT ["su", "-", "user"]` to allow `su` to properly set up supplementary groups.

containerd is an open source container runtime. Before versions 1.6.18 and 1.5.18, when importing an OCI image, there was no limit on the number of bytes read for certain files. A maliciously crafted image with a large file where a limit was not applied could cause a denial of service. This bug has been fixed in containerd 1.6.18 and 1.5.18. Users should update to these versions to resolve the issue. As a workaround, ensure that only trusted images are used and that only trusted users have permissions to import images.

containerd is an open source container runtime. A bug was found in containerd's CRI implementation where a user can exhaust memory on the host. In the CRI stream server, a goroutine is launched to handle terminal resize events if a TTY is requested. If the user's process fails to launch due to, for example, a faulty command, the goroutine will be stuck waiting to send without a receiver, resulting in a memory leak. Kubernetes and crictl can both be configured to use containerd's CRI implementation and the stream server is used for handling container IO. This bug has been fixed in containerd 1.6.12 and 1.5.16. Users should update to these versions to resolve the issue. Users unable to upgrade should ensure that only trusted images and commands are used and that only trusted users have permissions to execute commands in running containers.

containerd is an open source container runtime. A bug was found in the containerd's CRI implementation where programs inside a container can cause the containerd daemon to consume memory without bound during invocation of the `ExecSync` API. This can cause containerd to consume all available memory on the computer, denying service to other legitimate workloads. Kubernetes and crictl can both be configured to use containerd's CRI implementation; `ExecSync` may be used when running probes or when executing processes via an "exec" facility. This bug has been fixed in containerd 1.6.6 and 1.5.13. Users should update to these versions to resolve the issue. Users unable to upgrade should ensure that only trusted images and commands are used.