I am breaking my head in Analyzing Container Filesystem Isolation For Multi-Tenant Workloads, so you don’t have to
Container filesystem isolation defaults protect well, but advanced features like bidirectional mount propagation or SELinux relabeling can create host compromise vectors. The kernel auto-demotes shared mounts to MS_SLAVE in less-privileged namespaces, and seccomp blocks mount() by default before AppArmor/SELinux enforcement. OverlayFS kernel bugs (CVE-2023-0386) bypass all container isolation. For untrusted multi-tenant workloads, consider gVisor or Firecracker/Kata instead of relying solely on namespace isolation.