Headline
GHSA-j26p-6wx7-f3pw: Youki: If /proc and /sys in the rootfs are symbolic links, they can potentially be exploited to gain access to the host root filesystem.
Summary
If /proc and /sys in the rootfs are symbolic links, they can potentially be exploited to gain access to the host root filesystem.
Details
For security reasons, container creation should be prohibited if /proc or /sys in the rootfs is a symbolic link.
I verified this behavior with youki.
When /proc or /sys is a symbolic link, runc fails to create the container, whereas youki successfully creates it.
This is the fix related to this issue in runc.
- https://github.com/opencontainers/runc/pull/3756
- https://github.com/opencontainers/runc/pull/3773
- https://github.com/opencontainers/runc/blob/main/libcontainer/rootfs_linux.go#L590
- https://github.com/opencontainers/runc/blob/main/tests/integration/mask.bats#L60
Impact
The following advisory appears to be related to this vulnerability:
- https://github.com/advisories/GHSA-vpvm-3wq2-2wvm
- https://github.com/advisories/GHSA-fh74-hm69-rqjw
Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.