Incorrect Permission Assignment for Critical Resource Affecting github.com/containerd/containerd/pkg/cri/server package, versions <1.5.11 >=1.6.0 <1.6.2

github.com/containerd/containerd/pkg/cri/server is an industry-standard container runtime with an emphasis on simplicity, robustness and portability. It is available as a daemon for Linux and Windows, which can manage the complete container lifecycle of its host system: image transfer and storage, container execution and supervision, low-level storage and network attachments, etc.

Affected versions of this package are vulnerable to Incorrect Permission Assignment for Critical Resource via containers that were incorrectly started with non-empty inheritable Linux process capabilities, creating an atypical Linux environment and enabling programs with inheritable file capabilities to elevate those capabilities to the permitted set during execve(2). Normally, when executable programs have specified permitted file capabilities, otherwise unprivileged users and processes can execute those programs and gain the specified file capabilities up to the bounding set. Due to this bug, containers which included executable programs with inheritable file capabilities allowed otherwise unprivileged users and processes to additionally gain these inheritable file capabilities up to the container's bounding set. Containers which use Linux users and groups to perform privilege separation inside the container are most directly impacted. This bug did not affect the container security sandbox as the inheritable set never contained more capabilities than were included in the container's bounding set. Running containers should be stopped, deleted, and recreated for the inheritable capabilities to be reset.

The entry point of a container can be modified to use a utility like capsh(1) to drop inheritable capabilities prior to the primary process starting.

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