Incus nil-pointer dereference in storage bucket import allows denial of service

Incus is a system container and virtual machine manager. In versions before 7.0.0, missing validation logic in the storage bucket import logic allows an authenticated user with access to the storage bucket feature to cause the Incus daemon to crash. The vulnerability is present in the backup metadata handling logic, where the daemon processes the index.yaml file from an imported archive and accesses members of the parsed backup configuration without first verifying that the configuration object was initialized. A malicious or malformed index.yaml that omits the config block causes a nil-pointer dereference during bucket import operations and terminates the daemon. Repeated use of this issue can be used to keep Incus offline, causing a denial of service. This issue is fixed in version 7.0.0.