Dropbear before 2017.75 might allow local users to read certain files as root, if the file has the authorized_keys file format with a command= option. This occurs because ~/.ssh/authorized_keys is read with root privileges and symlinks are followed.
https://security.netapp.com/advisory/ntap-20191004-0006/
http://www.debian.org/security/2017/dsa-3859
http://lists.ucc.gu.uwa.edu.au/pipermail/dropbear/2017q2/001985.html