There are 3 open security issues in buster.
1 important issue:
runc before 1.0.0-rc95 allows a Container Filesystem Breakout via Directory Traversal. To exploit the vulnerability, an attacker must be able to create multiple containers with a fairly specific mount configuration. The problem occurs via a symlink-exchange attack that relies on a race condition.
2 issues left for the package maintainer to handle:
runc through 1.0.0-rc8, as used in Docker through 19.03.2-ce and other products, allows AppArmor restriction bypass because libcontainer/rootfs_linux.go incorrectly checks mount targets, and thus a malicious Docker image can mount over a /proc directory.
runc through 1.0.0-rc9 has Incorrect Access Control leading to Escalation of Privileges, related to libcontainer/rootfs_linux.go. To exploit this, an attacker must be able to spawn two containers with custom volume-mount configurations, and be able to run custom images. (This vulnerability does not affect Docker due to an implementation detail that happens to block the attack.)
You can find information about how to handle these issues in the security team's documentation.