[dwattttt]

I'm no expert, but the kernel is shared between all containers and the host.

I don't believe the kernel maintains separate page caches for each container; a malicious CI job could corrupt a binary from any container, or the host.

[firesteelrain]

Only if there is a shared inode between host and container.

[duped]

Which is almost guaranteed if you're launching multiple containers with the same base image or shared layers.