The dbclient in Dropbear SSH before 2016.74 allows remote attackers to execute arbitrary code via a crafted (1) -m or (2) -c argument.
https://security.gentoo.org/glsa/201702-23
https://secure.ucc.asn.au/hg/dropbear/rev/eed9376a4ad6
https://bugzilla.redhat.com/show_bug.cgi?id=1376353