What it means
Container runtime isolation constrains containers through namespaces, cgroups, capabilities, syscall controls, user separation, and hardened runtime configuration rather than assuming an image boundary is sufficient.
Why it matters
Containers share a kernel, so runtime choices determine whether a compromised workload remains confined or can affect neighboring containers and the host.
Practical focus
- Define the runtime privileges and host resources available to each container and the security outcome it must support
- Apply rootless or least-privileged execution, constrained capabilities, and approved runtime settings through documented, reviewable configuration
- Verify effective runtime configuration, escape indicators, and privileged-container use after changes and on a scheduled basis
- Plan for a compatibility request leading to host-level privilege or isolation failure, including rollback, ownership, and escalation
Common mistakes
- Enabling a feature without defining what it should protect
- Relying on defaults or one-time validation
- Granting broad exceptions that erase the control boundary
- Treating a compatibility request leading to host-level privilege or isolation failure as an operational surprise instead of a test case
Certification relevance
This subject appears in or supports the following certification bodies of knowledge: