scponly 4.6 and earlier allows remote authenticated users to bypass intended restrictions and execute code by invoking dangerous subcommands including (1) unison, (2) rsync, (3) svn, and (4) svnserve, as originally demonstrated by creating a Subversion (SVN) repository with malicious hooks, then using svn to trigger execution of those hooks.
https://www.redhat.com/archives/fedora-package-announce/2008-February/msg00595.html
https://www.redhat.com/archives/fedora-package-announce/2008-February/msg00546.html
http://www.vupen.com/english/advisories/2007/4243
http://www.securitytracker.com/id?1019103
http://www.securityfocus.com/bid/26900
http://www.debian.org/security/2008/dsa-1473
http://security.gentoo.org/glsa/glsa-200802-06.xml
http://secunia.com/advisories/28981
http://secunia.com/advisories/28944
http://secunia.com/advisories/28538
http://secunia.com/advisories/28123
http://scponly.cvs.sourceforge.net/scponly/scponly/SECURITY?view=markup