A bug was found in Moby (Docker Engine) where attempting to copy files using docker cp into a specially-crafted container can result in Unix file permission changes for existing files in the host’s filesystem, widening access to others. This bug does not directly allow files to be read, modified, or executed without an additional cooperating process.
This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers do not need to be restarted.