The dropbearconvert command in Dropbear SSH before 2016.74 allows attackers to execute arbitrary code via a crafted OpenSSH key file.
https://security.gentoo.org/glsa/201702-23
https://secure.ucc.asn.au/hg/dropbear/rev/34e6127ef02e
https://bugzilla.redhat.com/show_bug.cgi?id=1376353