An incorrect permission assignment flaw was found in containerd. This flaw allows a local attacker to use a specially designed text file to read and write files outside of the container's scope.
Impact A bug was found in containerd where container root directories and some plugins had insufficiently restricted permissions, allowing otherwise unprivileged Linux users to traverse directory contents and execute programs. When containers included executable programs with extended permission bits (such as setuid), unprivileged Linux users could discover and execute those programs. When the UID of an unprivileged Linux user on the host collided with the file owner or group inside a container, the unprivileged Linux user on the host could discover, read, and modify those files.
Patches This vulnerability has been fixed in containerd 1.4.11 and containerd 1.5.7. Users should update to these version when they are released and may restart containers or update directory permissions to mitigate the vulnerability.
Workarounds Limit access to the host to trusted users. Update directory permission on container bundles directories.
For more information If you have any questions or comments about this advisory: Open an issue in github.com/containerd/containerd Email us at security@containerd.io
Impact
A bug was found in containerd where containers launched through containerd’s CRI implementation with a specially-crafted image configuration could gain access to read-only copies of arbitrary files and directories on the host. This may bypass any policy-based enforcement on container setup (including a Kubernetes Pod Security Policy) and expose potentially sensitive information. Kubernetes and crictl can both be configured to use containerd’s CRI implementation.
Patches
This bug has been fixed in containerd 1.6.1, 1.5.10 and 1.4.13. Users should update to these versions to resolve the issue.
Workarounds
Ensure that only trusted images are used.
Credits
The containerd project would like to thank Felix Wilhelm of Google Project Zero for responsibly disclosing this issue in accordance with the containerd security policy.
For more information
If you have any questions or comments about this advisory:
Open an issue in containerd Email us at security@containerd.io
Impact
A bug was found in containerd where pulling and extracting a specially-crafted container image can result in Unix file permission changes for existing files in the host’s filesystem. Changes to file permissions can deny access to the expected owner of the file, widen access to others, or set extended bits like setuid, setgid, and sticky. This bug does not directly allow files to be read, modified, or executed without an additional cooperating process.
Patches
This bug has been fixed in containerd 1.5.4 and 1.4.8. Users should update to these versions as soon as they are released. Running containers do not need to be restarted.
Workarounds
Ensure you only pull images from trusted sources.
Linux security modules (LSMs) like SELinux and AppArmor can limit the files potentially affected by this bug through policies and profiles that prevent containerd from interacting with unexpected files.
For more information
If you have any questions or comments about this advisory:
Open an issue Email us at security@containerd.io if you think you’ve found a security bug.