Dropbear before 2017.75 might allow local users to read certain files as root, if the file has the authorizedkeys file format with a command= option. This occurs because ~/.ssh/authorizedkeys is read with root privileges and symlinks are followed.
{ "binaries": [ { "binary_name": "dropbear", "binary_version": "2016.72-1" }, { "binary_name": "dropbear-bin", "binary_version": "2016.72-1" }, { "binary_name": "dropbear-initramfs", "binary_version": "2016.72-1" }, { "binary_name": "dropbear-run", "binary_version": "2016.72-1" } ] }