Sendmail Consortium's Restricted Shell (SMRSH) in Sendmail 8.12.6, 8.11.6-15, and possibly other versions after 8.11 from 5/19/1998, allows attackers to bypass the intended restrictions of smrsh by inserting additional commands after (1) "||" sequences or (2) "/" characters, which are not properly filtered or verified.
http://www.redhat.com/support/errata/RHSA-2003-073.html
http://www.mandriva.com/security/advisories?name=MDKSA-2002:083
http://www.iss.net/security_center/static/10232.php
http://secunia.com/advisories/7826
http://marc.info/?l=bugtraq&m=103350914307274&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000532