Package Instance

Clarify Content-Type handling
### Impact
In the OCI Distribution Specification version 1.0.0 and prior, the Content-Type header alone was used to determine the type of document during push and pull operations. Documents that contain both “manifests” and “layers” fields could be interpreted as either a manifest or an index in the absence of an accompanying Content-Type header. If a Content-Type header changed between two pulls of the same digest, a client may interpret the resulting content differently.

### Patches
The OCI Distribution Specification will be updated to require that a `mediaType` value present in a manifest or index match the Content-Type header used during the push and pull operations.

### Workarounds
Clients pulling from a registry may distrust the Content-Type header and reject an ambiguous document that contains both “manifests” and “layers” fields or “manifests” and “config” fields.

### References
https://github.com/opencontainers/image-spec/security/advisories/GHSA-77vh-xpmg-72qh

### For more information
If you have any questions or comments about this advisory:
* Open an issue in https://github.com/opencontainers/distribution-spec/
* Email us at security@opencontainers.org

Insufficiently restricted permissions on plugin directories
### 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](https://github.com/containerd/containerd/issues/new/choose)
* Email us at [security@containerd.io](mailto:security@containerd.io)