Proxmox -> LXC -> Docker
runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7, 1.3.2 and 1.4.0-rc.2, an attacker can trick runc into misdirecting writes to /proc to other procfs files through the use of a racing container with shared mounts (we have also verified this attack is possible to exploit using a standard Dockerfile with docker buildx build as that also permits triggering parallel execution of containers with custom shared mounts configured). This redirect could be through symbolic links in a tmpfs or theoretically other methods such as regular bind-mounts. While similar, the mitigation applied for the related CVE, CVE-2019-19921, was fairly limited and effectively only caused runc to verify that when LSM labels are written they are actually procfs files. This issue is fixed in versions 1.2.8, 1.3.3, and 1.4.0-rc.3.
openconatiners/runc issue #4968
This is caused by a design flaw in AppArmor when running runc (or Docker/Podman/containerd) inside a nested container that has an AppArmor profile applied (the very short explanation is that AppArmor incorrectly thinks that when runc accesses
/proc/sys/...that it is accessing/sys/...and it rejects the access attempt because it violates the configured AppArmor policy).
Patch Info
lxc-pve (6.0.5-2) has a fix in it
Downgrade Fix
This fix is not recommended for systems that allow users to start their own containers
| Status | Version |
|---|---|
| Working version | 1.7.29-1~debian.12~bookworm |
| Broken version | 1.7.29-2~debian.12~bookworm |